Fix dependencies between subpackages

New macros backported from Fedora/EPEL

Strip tildes from %version in %pypi_source by default
Resolves: rhbz#1844902

Fix the %py_build macro to respect the global definition of %__python
Resolves: rhbz#1757833

Workaround leaking buildroot PATH in %py_byte_compile
Resolves: rhbz#1644455

Make %py_byte_compile terminate build on SyntaxErrors
Resolves: rhbz#1620168

Disable the python_provide macro for `python2-` prefixed packages
Resolves: rhbz#1636029

macros.pybytecompile: Macro was not line-continued properly and thus didn't work

macros.pybytecompile: Detect Python version through sys.version_info instead

Merging: (Tue Jul 10 2018 Tomas Orsava <torsava@redhat.com> - 3-32)
Fix %py_byte_compile macro: when invoked with a Python 2 binary it also
Merging: (Tue Jul 03 2018 Miro Hrončok <mhroncok@redhat.com> - 3-31)
Add %python3_platform useful for PYTHONPATH on arched builds
Merging: (Mon Jun 18 2018 Jason L Tibbitts III <tibbs@math.uh.edu> - 3-30)
Add %pypi_source macro, as well as %__pypi_url and
Merging: (Wed Apr 18 2018 Miro Hrončok <mhroncok@redhat.com> - 3-29)
move macros.pybytecompile from python3-devel

Remove RHEL_ALLOW_PYTHON2_FOR_BUILD=1 from build and install macros,

Explicitly enable Python 2 when invoking Python 2 macros
py2

Switch the Python 3 executable to /usr/libexec/platform-python
Update macros using pip or easy_install to be invoked through the main

Fix the %py_dist_name macro to not convert dots (".") into dashes, so that

make LDFLAGS propagated whenever CFLAGS are

Rebuilt for https://fedoraproject.org/wiki/Fedora_28_Mass_Rebuild