Merge branch 'athsimulation_pymodules' into 'master'

AthSimulationExternals: Add PyModules and flake8_atlas

See merge request !505

Projects/AthSimulationExternals/package_filters.txt

-# Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
 #
 # List of packages to build as part of AthSimulationExternals.
 #
@@ -11,7 +11,9 @@
 + External/GoogleTest
 + External/HepMCAnalysis
 + External/MKL
++ External/PyModules
 + External/dSFMT
++ External/flake8_atlas
 + External/nlohmann_json
 + External/prmon
 + External/yampl