Changes

Remove all imports of print_function compatibility method

Remove all imports of division compatibility method

Remove all imports of absolute_import compatibility method

Replace all usages of native_str compatibility method

Replace all usages of standard_library compatibility method

Replace all usages of old_div

For numerical division, use / when the result is expected to be
a float or // when the floor division is desired
For path concatenation, use / systematically

Replace usage of past.builtins.execfile by exec

Replace all usages of past.builtins.basestring by str

Replace all usages of past.builtins.long

Review and cleanup all codepaths handling Python 2

Remove all unnecessary builtins imports

Fix miscellaneous flake8 warnings

Fix exec invocation for training scripts

OMERO.web integration tests: expect timestamp without milliseconds

build with various Python version

cap setuptools

fix badge display