Fix long-standing bug where directories inside the "python" dir were not handled correctly.
e.g. Configuration.Generator.Herwig7Settings.Herwig7LHECommonSettings_cfi
now goes to
Configuration/Generator/python/Herwig7Settings/Herwig7LHECommonSettings_cfi.py
instead of
Configuration/Generator/Herwig7Settings/python/Herwig7LHECommonSettings_cfi.py