diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 710369b6c7..8c3f7591e5 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -88,6 +88,8 @@ Added
   Contributed by @cognifloyd
 * Allow `st2-rule-tester` to run without a mongo connection if user is testing against local `rule`/`trigger-instance` files. #6208
   Contributed by @jk464
+* Added `certificate` parameter to the base SSH runners to enable certificate-based ssh authentication. #6347
+  Contributed by @freddierice
 
 * Added a `get_result` method to the `ExecutionResourceManager` Class for st2client
   Contributed by @skiedude
diff --git a/contrib/runners/python_runner/python_runner/python_runner.py b/contrib/runners/python_runner/python_runner/python_runner.py
index a8200e0bb3..99723765c2 100644
--- a/contrib/runners/python_runner/python_runner/python_runner.py
+++ b/contrib/runners/python_runner/python_runner/python_runner.py
@@ -92,7 +92,6 @@ def __init__(
         sandbox=True,
         use_parent_args=True,
     ):
-
         """
         :param timeout: Action execution timeout in seconds.
         :type timeout: ``int``
diff --git a/lockfiles/st2.lock b/lockfiles/st2.lock
index 7b5ab4a8b4..084352d1e0 100644
--- a/lockfiles/st2.lock
+++ b/lockfiles/st2.lock
@@ -5741,7 +5741,7 @@
           "artifacts": [
             {
               "algorithm": "sha256",
-              "hash": "e49a85b9d1ad7cd9e75d53810ddf1e3ec50c83b1e4d8629d80f0566a233e5637",
+              "hash": "d34d5cbb539182553ec8b35a0763decb6b66bd37aa51f3a61db1eb30449f6f10",
               "url": "git+https://github.com/StackStorm/st2-rbac-backend.git@master"
             }
           ],
diff --git a/st2actions/tests/unit/test_paramiko_ssh.py b/st2actions/tests/unit/test_paramiko_ssh.py
index d60c227b1d..174365e609 100644
--- a/st2actions/tests/unit/test_paramiko_ssh.py
+++ b/st2actions/tests/unit/test_paramiko_ssh.py
@@ -640,9 +640,9 @@ def test_consume_stdout(self):
         chan = Mock()
         chan.recv_ready.side_effect = [True, True, True, True, False]
 
-        chan.recv.side_effect = [b"\xF0", b"\x90", b"\x8D", b"\x88"]
+        chan.recv.side_effect = [b"\xf0", b"\x90", b"\x8d", b"\x88"]
         try:
-            b"\xF0".decode("utf-8")
+            b"\xf0".decode("utf-8")
             self.fail("Test fixture is not right.")
         except UnicodeDecodeError:
             pass
@@ -666,9 +666,9 @@ def test_consume_stderr(self):
         chan = Mock()
         chan.recv_stderr_ready.side_effect = [True, True, True, True, False]
 
-        chan.recv_stderr.side_effect = [b"\xF0", b"\x90", b"\x8D", b"\x88"]
+        chan.recv_stderr.side_effect = [b"\xf0", b"\x90", b"\x8d", b"\x88"]
         try:
-            b"\xF0".decode("utf-8")
+            b"\xf0".decode("utf-8")
             self.fail("Test fixture is not right.")
         except UnicodeDecodeError:
             pass
diff --git a/st2api/st2api/controllers/v1/actionalias.py b/st2api/st2api/controllers/v1/actionalias.py
index 5488300d6e..1c4b7b4a59 100644
--- a/st2api/st2api/controllers/v1/actionalias.py
+++ b/st2api/st2api/controllers/v1/actionalias.py
@@ -112,7 +112,7 @@ def help(self, filter, pack, limit, offset, **kwargs):
             return generate_helpstring_result(
                 aliases, filter, pack, int(limit), int(offset)
             )
-        except (TypeError) as e:
+        except TypeError as e:
             LOG.exception(
                 "Helpstring request contains an invalid data type: %s.",
                 six.text_type(e),
diff --git a/st2api/st2api/controllers/v1/triggers.py b/st2api/st2api/controllers/v1/triggers.py
index 4082490e13..5945d670c7 100644
--- a/st2api/st2api/controllers/v1/triggers.py
+++ b/st2api/st2api/controllers/v1/triggers.py
@@ -244,7 +244,6 @@ class TriggerController(object):
     """
 
     def get_one(self, trigger_id):
-
         """
         List trigger by id.
 
diff --git a/st2client/st2client/commands/action.py b/st2client/st2client/commands/action.py
index 48964746a5..6f470dbac0 100644
--- a/st2client/st2client/commands/action.py
+++ b/st2client/st2client/commands/action.py
@@ -878,7 +878,7 @@ def transform_array(value, action_params=None, auto_dict=False):
             # the 'result' to the dict type value.
             if all([isinstance(x, str) and ":" in x for x in result]) and auto_dict:
                 result_dict = {}
-                for (k, v) in [x.split(":") for x in result]:
+                for k, v in [x.split(":") for x in result]:
                     # To parse values using the 'transformer' according to the type which is
                     # specified in the action metadata, calling 'normalize' method recursively.
                     if (
diff --git a/st2client/st2client/commands/trace.py b/st2client/st2client/commands/trace.py
index 57152644c3..4fdfc72e66 100644
--- a/st2client/st2client/commands/trace.py
+++ b/st2client/st2client/commands/trace.py
@@ -74,9 +74,11 @@ def __init__(self, description, app, subparsers, parent_parser=None):
 class SingleTraceDisplayMixin(object):
     def print_trace_details(self, trace, args, **kwargs):
         options = {
-            "attributes": TRACE_ATTRIBUTE_DISPLAY_ORDER
-            if args.json
-            else TRACE_HEADER_DISPLAY_ORDER
+            "attributes": (
+                TRACE_ATTRIBUTE_DISPLAY_ORDER
+                if args.json
+                else TRACE_HEADER_DISPLAY_ORDER
+            )
         }
         options["json"] = args.json
         options["yaml"] = args.yaml
diff --git a/st2common/st2common/cmd/validate_api_spec.py b/st2common/st2common/cmd/validate_api_spec.py
index 0a9facd9c1..a5ccdeae11 100644
--- a/st2common/st2common/cmd/validate_api_spec.py
+++ b/st2common/st2common/cmd/validate_api_spec.py
@@ -69,7 +69,7 @@ def _validate_definitions(spec):
     error = False
     verbose = cfg.CONF.verbose
 
-    for (model, definition) in six.iteritems(defs):
+    for model, definition in six.iteritems(defs):
         api_model = definition.get("x-api-model", None)
 
         if not api_model:
diff --git a/st2common/st2common/content/loader.py b/st2common/st2common/content/loader.py
index 582834a45d..cb2bf82302 100644
--- a/st2common/st2common/content/loader.py
+++ b/st2common/st2common/content/loader.py
@@ -295,7 +295,6 @@ class OverrideLoader(object):
     DEFAULT_OVERRIDE_VALUES = {"enabled": True}
 
     def override(self, pack_name, resource_type, content):
-
         """
         Loads override content for pack, and updates content
 
@@ -340,7 +339,6 @@ def override(self, pack_name, resource_type, content):
     def _apply_override_file(
         self, override_file, pack_name, resource_type, content, global_file
     ):
-
         """
         Loads override content from override file
 
diff --git a/st2common/st2common/expressions/functions/time.py b/st2common/st2common/expressions/functions/time.py
index d25b8acecc..01d8fa9ad5 100644
--- a/st2common/st2common/expressions/functions/time.py
+++ b/st2common/st2common/expressions/functions/time.py
@@ -63,7 +63,7 @@ def _get_human_time(seconds):
         return "0s"
 
     if seconds < 1:
-        return "%s\u03BCs" % seconds  # Microseconds
+        return "%s\u03bcs" % seconds  # Microseconds
 
     if isinstance(seconds, float):
         seconds = long_int(round(seconds))  # Let's lose microseconds.
diff --git a/st2common/st2common/fields.py b/st2common/st2common/fields.py
index 0e94f11f85..66337476fb 100644
--- a/st2common/st2common/fields.py
+++ b/st2common/st2common/fields.py
@@ -458,6 +458,7 @@ def _serialize_field_value(self, value: dict) -> bytes:
         """
         Serialize and encode the provided field value.
         """
+
         # Orquesta workflows support toSet() YAQL operator which returns a set which used to get
         # serialized to list by mongoengine DictField.
         #
diff --git a/st2common/st2common/middleware/logging.py b/st2common/st2common/middleware/logging.py
index 66df246537..bd91351bc6 100644
--- a/st2common/st2common/middleware/logging.py
+++ b/st2common/st2common/middleware/logging.py
@@ -112,9 +112,9 @@ def custom_start_response(status, headers, exc_info=None):
             "remote_addr": request.remote_addr,
             "status": status_code[0],
             "runtime": float("{0:.3f}".format((clock() - start_time) * 10**3)),
-            "content_length": content_length[0]
-            if content_length
-            else len(b"".join(retval)),
+            "content_length": (
+                content_length[0] if content_length else len(b"".join(retval))
+            ),
             "request_id": request.headers.get(REQUEST_ID_HEADER, None),
         }
 
diff --git a/st2common/st2common/models/system/action.py b/st2common/st2common/models/system/action.py
index 77a110394d..db8de3de6a 100644
--- a/st2common/st2common/models/system/action.py
+++ b/st2common/st2common/models/system/action.py
@@ -309,7 +309,7 @@ def _get_script_arguments(self, named_args=None, positional_args=None):
 
         # add all named_args in the format <kwarg_op>name=value (e.g. --name=value)
         if named_args is not None:
-            for (arg, value) in six.iteritems(named_args):
+            for arg, value in six.iteritems(named_args):
                 if value is None or (
                     isinstance(value, (str, six.text_type)) and len(value) < 1
                 ):
diff --git a/st2common/st2common/router.py b/st2common/st2common/router.py
index 1200044fd6..cd9a25d7bf 100644
--- a/st2common/st2common/router.py
+++ b/st2common/st2common/router.py
@@ -241,11 +241,11 @@ def add_spec(self, spec, transforms):
         validate(fast_deepcopy_dict(self.spec))
 
         for filter in transforms:
-            for (path, methods) in six.iteritems(spec["paths"]):
+            for path, methods in six.iteritems(spec["paths"]):
                 if not re.search(filter, path):
                     continue
 
-                for (method, endpoint) in six.iteritems(methods):
+                for method, endpoint in six.iteritems(methods):
                     conditions = {"method": [method.upper()]}
 
                     connect_kw = {}
diff --git a/st2common/st2common/runners/parallel_ssh.py b/st2common/st2common/runners/parallel_ssh.py
index 9aee991b0c..5e4e590ecf 100644
--- a/st2common/st2common/runners/parallel_ssh.py
+++ b/st2common/st2common/runners/parallel_ssh.py
@@ -46,6 +46,7 @@ def __init__(
         password=None,
         pkey_file=None,
         pkey_material=None,
+        pkey_certificate=None,
         port=22,
         bastion_host=None,
         concurrency=10,
@@ -68,6 +69,7 @@ def __init__(
         self._ssh_user = user
         self._ssh_key_file = pkey_file
         self._ssh_key_material = pkey_material
+        self._ssh_key_certificate = pkey_certificate
         self._ssh_password = password
         self._hosts = hosts
         self._successful_connects = 0
@@ -270,6 +272,7 @@ def _connect(self, host, results, raise_on_any_error=False):
             bastion_host=self._bastion_host,
             key_files=self._ssh_key_file,
             key_material=self._ssh_key_material,
+            key_certificate=self._ssh_key_certificate,
             passphrase=self._passphrase,
             handle_stdout_line_func=self._handle_stdout_line_func,
             handle_stderr_line_func=self._handle_stderr_line_func,
diff --git a/st2common/st2common/runners/paramiko_ssh.py b/st2common/st2common/runners/paramiko_ssh.py
index df1c492e89..372c52ca66 100644
--- a/st2common/st2common/runners/paramiko_ssh.py
+++ b/st2common/st2common/runners/paramiko_ssh.py
@@ -102,6 +102,7 @@ def __init__(
         bastion_host=None,
         key_files=None,
         key_material=None,
+        key_certificate=None,
         timeout=None,
         passphrase=None,
         handle_stdout_line_func=None,
@@ -125,6 +126,7 @@ def __init__(
         self.key_files = key_files
         self.timeout = timeout
         self.key_material = key_material
+        self.key_certificate = key_certificate
         self.bastion_host = bastion_host
         self.passphrase = passphrase
         self.ssh_connect_timeout = cfg.CONF.ssh_runner.ssh_connect_timeout
@@ -628,7 +630,7 @@ def _get_decoded_data(self, data):
             self.logger.exception("Non UTF-8 character found in data: %s", data)
             raise
 
-    def _get_pkey_object(self, key_material, passphrase):
+    def _get_pkey_object(self, key_material, passphrase, key_certificate=None):
         """
         Try to detect private key type and return paramiko.PKey object.
         """
@@ -636,6 +638,8 @@ def _get_pkey_object(self, key_material, passphrase):
         for cls in [paramiko.RSAKey, paramiko.DSSKey, paramiko.ECDSAKey]:
             try:
                 key = cls.from_private_key(StringIO(key_material), password=passphrase)
+                if key_certificate:
+                    key.load_certificate(key_certificate)
             except paramiko.ssh_exception.SSHException:
                 # Invalid key, try other key type
                 pass
@@ -758,7 +762,9 @@ def _connect(self, host, socket=None):
 
         if self.key_material:
             conninfo["pkey"] = self._get_pkey_object(
-                key_material=self.key_material, passphrase=self.passphrase
+                key_material=self.key_material,
+                passphrase=self.passphrase,
+                key_certificate=self.key_certificate,
             )
 
         if not self.password and not (self.key_files or self.key_material):
diff --git a/st2common/st2common/runners/paramiko_ssh_runner.py b/st2common/st2common/runners/paramiko_ssh_runner.py
index f41882935f..0794cfbee6 100644
--- a/st2common/st2common/runners/paramiko_ssh_runner.py
+++ b/st2common/st2common/runners/paramiko_ssh_runner.py
@@ -38,6 +38,7 @@
 RUNNER_USERNAME = "username"
 RUNNER_PASSWORD = "password"
 RUNNER_PRIVATE_KEY = "private_key"
+RUNNER_CERTIFICATE = "certificate"
 RUNNER_PARALLEL = "parallel"
 RUNNER_SUDO = "sudo"
 RUNNER_SUDO_PASSWORD = "sudo_password"
@@ -64,6 +65,7 @@ def __init__(self, runner_id):
         self._username = None
         self._password = None
         self._private_key = None
+        self._certificate = None
         self._passphrase = None
         self._kwarg_op = "--"
         self._cwd = None
@@ -93,6 +95,7 @@ def pre_run(self):
         self._username = self.runner_parameters.get(RUNNER_USERNAME, None)
         self._password = self.runner_parameters.get(RUNNER_PASSWORD, None)
         self._private_key = self.runner_parameters.get(RUNNER_PRIVATE_KEY, None)
+        self._certificate = self.runner_parameters.get(RUNNER_CERTIFICATE, None)
         self._passphrase = self.runner_parameters.get(RUNNER_PASSPHRASE, None)
 
         self._ssh_port = self.runner_parameters.get(RUNNER_SSH_PORT, None)
@@ -200,6 +203,9 @@ def store_stderr_line(line):
             # Default to stanley key file specified in the config
             client_kwargs["pkey_file"] = self._ssh_key_file
 
+        if self._certificate:
+            client_kwargs["pkey_certificate"] = self._certificate
+
         if self._sudo_password:
             client_kwargs["sudo_password"] = True
 
diff --git a/st2common/st2common/util/file_system.py b/st2common/st2common/util/file_system.py
index e26adaedfd..b698ace803 100644
--- a/st2common/st2common/util/file_system.py
+++ b/st2common/st2common/util/file_system.py
@@ -59,7 +59,7 @@ def include_file(file_path):
 
         return True
 
-    for (dirpath, dirnames, filenames) in os.walk(directory):
+    for dirpath, dirnames, filenames in os.walk(directory):
         base_path = dirpath.replace(directory, "")
 
         for filename in filenames:
diff --git a/st2common/st2common/util/mongoescape.py b/st2common/st2common/util/mongoescape.py
index 56c4d18744..d0d657a720 100644
--- a/st2common/st2common/util/mongoescape.py
+++ b/st2common/st2common/util/mongoescape.py
@@ -32,7 +32,7 @@
 
 # http://docs.mongodb.org/manual/faq/developers/#faq-dollar-sign-escaping
 UNESCAPED = [".", "$"]
-ESCAPED = ["\uFF0E", "\uFF04"]
+ESCAPED = ["\uff0e", "\uff04"]
 ESCAPE_TRANSLATION = dict(list(zip(UNESCAPED, ESCAPED)))
 UNESCAPE_TRANSLATION = dict(
     list(zip(ESCAPED, UNESCAPED))
diff --git a/st2common/st2common/util/virtualenvs.py b/st2common/st2common/util/virtualenvs.py
index 3326c18fe0..bda087163f 100644
--- a/st2common/st2common/util/virtualenvs.py
+++ b/st2common/st2common/util/virtualenvs.py
@@ -62,7 +62,6 @@ def setup_pack_virtualenv(
     force_owner_group=True,
     inject_parent_virtualenv_sites=True,
 ):
-
     """
     Setup virtual environment for the provided pack.
 
diff --git a/st2common/tests/unit/test_time_jinja_filters.py b/st2common/tests/unit/test_time_jinja_filters.py
index b7e461e64b..276716ab9b 100644
--- a/st2common/tests/unit/test_time_jinja_filters.py
+++ b/st2common/tests/unit/test_time_jinja_filters.py
@@ -22,7 +22,7 @@
 class TestTimeJinjaFilters(TestCase):
     def test_to_human_time_from_seconds(self):
         self.assertEqual("0s", time.to_human_time_from_seconds(seconds=0))
-        self.assertEqual("0.1\u03BCs", time.to_human_time_from_seconds(seconds=0.1))
+        self.assertEqual("0.1\u03bcs", time.to_human_time_from_seconds(seconds=0.1))
         self.assertEqual("56s", time.to_human_time_from_seconds(seconds=56))
         self.assertEqual("56s", time.to_human_time_from_seconds(seconds=56.2))
         self.assertEqual("7m36s", time.to_human_time_from_seconds(seconds=456))
diff --git a/st2reactor/st2reactor/rules/filter.py b/st2reactor/st2reactor/rules/filter.py
index f2b4c7b753..1bcf3a8506 100644
--- a/st2reactor/st2reactor/rules/filter.py
+++ b/st2reactor/st2reactor/rules/filter.py
@@ -95,7 +95,7 @@ def filter(self):
             extra=self._base_logger_context,
         )
 
-        for (criterion_k, criterion_v) in six.iteritems(criteria):
+        for criterion_k, criterion_v in six.iteritems(criteria):
             (
                 is_rule_applicable,
                 payload_value,
diff --git a/tools/st2-analyze-links.py b/tools/st2-analyze-links.py
index f66c158dea..ad4fb4aceb 100644
--- a/tools/st2-analyze-links.py
+++ b/tools/st2-analyze-links.py
@@ -99,7 +99,7 @@ def analyze(self, root_action_ref, link_tigger_ref):
                 )
             )
         analyzed = self._do_analyze(action_ref=root_action_ref)
-        for (depth, rule_link) in analyzed:
+        for depth, rule_link in analyzed:
             print("%s%s" % ("  " * depth, rule_link))
         return analyzed