Missing entry in SOURCES.txt

[Christoph Mathys <eraserix@gmail.com>]

I try to package mercurial-keyring. However, if I build the binary 
package and then try to build the source package, this process fails 
because SOURCES.txt has been modified by the binary package build.

Apparently, dh_python2 (setuptools) creates an entry in SOURCES.txt for 
setup.cfg. This entry is missing from the upstream packages SOURCES.txt.

Strange enough, on my ubuntu 12.04 box, running 'python setup.py sdist' 
does not add setup.cfg to SOURCES.txt. If an explicit 'python setup.py 
egg_info' is executed, this will add the missing entry.

What is the proposed solution here? Patch SOURCES.txt? Nag upstream to 
update to a newer setuptools-package?

Thanks!
Christoph