Python3 compliance
Skip pygrapes.adapter.Zmq tests if ZMQ library is not present
Load resources by absolute path not relative
Removed unused import
Load 'mock' mocking library
Removed unused 'mox' module
Python3 compliance
Python3 compliance
Fixed tests after removing 'message' attribute from exception message generated by Grape.format_exception
Load 'mock' module to core_test
Python3 compliance
Refactored code in order not to create unnecessary variables
Refactored core_test test suite to use 'mock' mocking library instead of mox