DEV: silence warnings from egg_info in scons.

`setup.py egg_info` is run from scons to update package version.
setup.py shows warnings when it cannot resolve boost_python name,
but that is not relevant for the `egg_info` command.

Author: pavoljuhas

src/extensions/SConscript

@@ -28,7 +28,7 @@ version = pyoutput(
     'print(versiondata.get("DEFAULT", "version"))\n' % basedir)
 egginfo = env.Command(NoCache('#/src/diffpy.srreal.egg-info/PKG-INFO'),
                       env.Value(version),
-                      '$python setup.py egg_info')
+                      '$python -Wignore setup.py egg_info')
 
 # install extension module in a development mode.
 develop = Alias('develop', [egginfo, Install('#/src/diffpy/srreal', module)])