pip install fails with gcc-c++-9.2.1

[abezyanka]

Minor issue, on fedora 31 with gcc-c++-9.2.1 the pip install fails due to syntax warning/errors.

Was able to work around it by adding to setup.py cmake_args:
'-DCMAKE_CXX_FLAGS=-Wno-error=parentheses'

Hopefully syntax can be corrected or the above added to avoid compilation errors.
Thank you :)

In file included from /tmp/pip-install-w3131icp/cppkin/build/temp.linux-x86_64-3.7/Third_Party/include/boost/mpl/aux_/na_assert.hpp:23,
                 from /tmp/pip-install-w3131icp/cppkin/build/temp.linux-x86_64-3.7/Third_Party/include/boost/mpl/arg.hpp:25,
                 from /tmp/pip-install-w3131icp/cppkin/build/temp.linux-x86_64-3.7/Third_Party/include/boost/variant/variant_fwd.hpp:19,
                 from /tmp/pip-install-w3131icp/cppkin/build/temp.linux-x86_64-3.7/Third_Party/include/boost/variant/variant.hpp:26,
                 from /tmp/pip-install-w3131icp/cppkin/build/temp.linux-x86_64-3.7/Third_Party/include/boost/variant.hpp:17,
                 from /tmp/pip-install-w3131icp/cppkin/src/BinaryAnnotation.h:5,
                 from /tmp/pip-install-w3131icp/cppkin/src/span_impl.h:10,
                 from /tmp/pip-install-w3131icp/cppkin/src/Span.h:5,
                 from /tmp/pip-install-w3131icp/cppkin/src/SpanContainer.h:7,
                 from /tmp/pip-install-w3131icp/cppkin/src/SpanContainer.cpp:2:
/tmp/pip-install-w3131icp/cppkin/build/temp.linux-x86_64-3.7/Third_Party/include/boost/mpl/assert.hpp:188:21: error: unnecessary parentheses in declaration of ‘assert_arg’ [-Werror=parentheses]
  188 | failed ************ (Pred::************
      |                     ^
/tmp/pip-install-w3131icp/cppkin/build/temp.linux-x86_64-3.7/Third_Party/include/boost/mpl/assert.hpp:193:21: error: unnecessary parentheses in declaration of ‘assert_not_arg’ [-Werror=parentheses]
  193 | failed ************ (boost::mpl::not_<Pred>::************
      |                     ^
cc1plus: all warnings being treated as errors

[dulikvor]

Thanks, i will review it :). feel free to provide a solution if you want and i will merge it :).