_codata.py varies between builds

[bmwiedemann]

While working on reproducible builds for openSUSE, I found that
our python-quantities package always had variations in _codata.py

This can be fixed with

--- a/setup.py
+++ b/setup.py
@@ -24,7 +24,6 @@ class data(Command):
         with open('quantities/constants/_codata.py', 'w') as f:
             f.write('# THIS FILE IS AUTOMATICALLY GENERATED\n')
             f.write('# ANY CHANGES MADE HERE WILL BE LOST\n')
-            f.write(f'# LAST GENERATED: {datetime.now()}\n\n')
             f.write('physical_constants = {}\n\n')
             for line in data:
                 name = line[:55].rstrip().replace('mag.','magnetic')

or with a more complex patch to allow to override the build date https://reproducible-builds.org/docs/source-date-epoch/#python