test_signal_crashes.py uses user's configuration file

The apport test_test_signal_crashes.py will read ~/.config/apport/settings and if you have the following in it:

[main]
unpackaged: True

Then the tests, unpackaged_binary and unpackaged_script at least, will fail because a .crash file ends up being created for those when they should not.

I tried resolving it by manually setting apport.fileutils._config_file but for some reason that too didn't work!

 $ bzr cdiff test/test_signal_crashes.py
=== modified file 'test/test_signal_crashes.py'
--- test/test_signal_crashes.py 2017-07-18 18:20:51 +0000
+++ test/test_signal_crashes.py 2017-10-27 17:05:28 +0000
@@ -48,6 +48,12 @@
         self.report_dir = tempfile.mkdtemp()
         os.environ['APPORT_REPORT_DIR'] = self.report_dir

+ # don't user user configuration
+ self.orig_config_file = apport.fileutils._config_file
+ f = tempfile.NamedTemporaryFile()
+ apport.fileutils._config_file = f.name
+ f.close()
+
         self.workdir = tempfile.mkdtemp()

         # move aside current ignore file
@@ -69,6 +75,9 @@
         shutil.rmtree(self.report_dir)
         shutil.rmtree(self.workdir)

+ # restore configuration
+ apport.fileutils._config_file = self.orig_config_file
+
         # clean up our ignore file
         if os.path.exists(ifpath):
             os.unlink(ifpath)