test_signals.py: Consistent test names
test_signals.py: Consistent test names

Use underscore style method/test case names consistently.

davibe/pygobject,GNOME/pygobject,GNOME/pygobject,davibe/pygobject,davibe/pygobject,davibe/pygobject,pexip/pygobject,sfeltman/pygobject,sfeltman/pygobject,pexip/pygobject,GNOME/pygobject,sfeltman/pygobject,pexip/pygobject