Tag to be used with the master branch of atlas/athena. Update(s) since 2.0.53: - Updated CheckerGccPlugins for GCC 10 compatibility; - Updated mergeConfdb2.py to handle gaudi handle properties correctly; - Marked the EXTRA_PATTERNS argument of atlas_add_test(...) deprecated; - Introduced FindPython.cmake into AtlasLCG; - Fixed a typo in the Acts build configuration.