Use string_required validator for content field

Also make the string_required validator trim
whitespace and then check that the string is
empty.

Author: samanehsan

framework/mongo/validators.py

@@ -6,7 +6,7 @@
 
 
 def string_required(value):
-    if value is None or value == '':
+    if value is None or value.strip() == '':
         raise ValidationValueError('Value must not be empty.')
     return True
 

tests/test_models.py

@@ -4160,7 +4160,7 @@ def test_create_comment_content_cannot_be_empty(self):
                 is_public=True,
                 content=''
         )
-        assert_equal(error.exception.message, 'Ensure this value is not empty.')
+        assert_equal(error.exception.message, 'Value must not be empty.')
 
     def test_create_comment_content_cannot_be_whitespace(self):
         with assert_raises(ValidationValueError) as error:
@@ -4172,7 +4172,7 @@ def test_create_comment_content_cannot_be_whitespace(self):
                 is_public=True,
                 content='    '
         )
-        assert_equal(error.exception.message, 'Ensure this value is not empty.')
+        assert_equal(error.exception.message, 'Value must not be empty.')
 
     def test_create_sends_comment_added_signal(self):
         with capture_signals() as mock_signals:

website/project/model.py

@@ -17,7 +17,7 @@
 
 from modularodm import Q
 from modularodm import fields
-from modularodm.validators import MaxLengthValidator, ValueNotEmptyValidator
+from modularodm.validators import MaxLengthValidator
 from modularodm.exceptions import NoResultsFound
 from modularodm.exceptions import ValidationTypeError
 from modularodm.exceptions import ValidationValueError
@@ -181,7 +181,7 @@ class Comment(GuidStoredObject):
 
     is_deleted = fields.BooleanField(default=False)
     content = fields.StringField(required=True,
-                                 validate=(MaxLengthValidator(settings.COMMENT_MAXLENGTH), ValueNotEmptyValidator()))
+                                 validate=[MaxLengthValidator(settings.COMMENT_MAXLENGTH), validators.string_required])
 
     # Dictionary field mapping user IDs to dictionaries of report details:
     # {