pyc generated files do not have matching timestamps

I don't know how waf generates the pyc files but current approach causes them being regenerated during first run:

[   99s] python-ntp.x86_64: W: python-bytecode-inconsistent-mtime /usr/lib64/python2.7/site-packages/ntp/magic.pyc 2017-05-21T12:00:00 /usr/lib64/python2.7/site-packages/ntp/magic.py 2017-05-21T18:00:03
[   99s] python-ntp.x86_64: W: python-bytecode-inconsistent-mtime /usr/lib64/python2.7/site-packages/ntp/control.pyc 2017-05-21T12:00:00 /usr/lib64/python2.7/site-packages/ntp/control.py 2017-05-21T18:00:03
[   99s] python-ntp.x86_64: W: python-bytecode-inconsistent-mtime /usr/lib64/python2.7/site-packages/ntp/version.pyc 2017-05-21T12:00:00 /usr/lib64/python2.7/site-packages/ntp/version.py 2017-05-21T18:00:04
[   99s] The timestamp embedded in this python bytecode file isn't equal to the mtime
[   99s] of the original source file, which will force the interpreter to recompile the
[   99s] .py source every time, ignoring the saved bytecode.

It is not much of a problem and I can workaround it in .spec file, but I guess it should be properly done in the buildsystem itself.