Move flake8 checking to build stage

Remove the separate flake8 unit test of the python directory and instead use the dedicated feature of atlas_install_python_modules.

Some of these tests were only checking new-style configuration, but that's already the default, so no separate test is needed.

Event/DumpEventDataToJSON/CMakeLists.txt

@@ -31,8 +31,4 @@ atlas_add_component( DumpEventDataToJSON
 
 # Install files from the package:
 atlas_install_joboptions( share/*.py )
-atlas_install_python_modules( python/*.py )
-
-atlas_add_test( flake8
- SCRIPT flake8 --select=ATL,F,E7,E9,W6 ${CMAKE_CURRENT_SOURCE_DIR}/python
- POST_EXEC_SCRIPT nopost.sh )
+atlas_install_python_modules( python/*.py POST_BUILD_CMD ${ATLAS_FLAKE8} )