Refactor TestCase files into python modules

Convert all TestCase files into standard python modules to be run and
discovered by unittest.

tests/signatures.TestCase

@@ -1,75 +0,0 @@
-#!/usr/bin/env python3
-
-import inspect
-import os
-import sys
-import unittest
-import hashlib
-import logging
-from tempfile import TemporaryDirectory
-
-localmodule = os.path.realpath(
-    os.path.join(os.path.dirname(inspect.getfile(inspect.currentframe())), '..')
-)
-print('localmodule: ' + localmodule)
-if localmodule not in sys.path:
-    sys.path.insert(0, localmodule)
-
-from testcommon import TmpCwd
-from fdroidserver import common, signatures
-
-
-class SignaturesTest(unittest.TestCase):
-    def setUp(self):
-        logging.basicConfig(level=logging.DEBUG)
-        common.config = None
-        config = common.read_config()
-        config['jarsigner'] = common.find_sdk_tools_cmd('jarsigner')
-        config['verbose'] = True
-        common.config = config
-
-    def test_main(self):
-
-        # option fixture class:
-        class OptionsFixture:
-            APK = [os.path.abspath(os.path.join('repo', 'com.politedroid_3.apk'))]
-
-        with TemporaryDirectory() as tmpdir, TmpCwd(tmpdir):
-            signatures.extract(OptionsFixture())
-
-            # check if extracted signatures are where they are supposed to be
-            # also verify weather if extracted file contian what they should
-            filesAndHashes = (
-                (os.path.join('metadata', 'com.politedroid', 'signatures', '3', 'MANIFEST.MF'),
-                 '7dcd83f0c41a75457fd2311bf3c4578f80d684362d74ba8dc52838d353f31cf2'),
-                (os.path.join('metadata', 'com.politedroid', 'signatures', '3', 'RELEASE.RSA'),
-                 '883ef3d5a6e0bf69d2a58d9e255a7930f08a49abc38e216ed054943c99c8fdb4'),
-                (os.path.join('metadata', 'com.politedroid', 'signatures', '3', 'RELEASE.SF'),
-                 '99fbb3211ef5d7c1253f3a7ad4836eadc9905103ce6a75916c40de2831958284'),
-            )
-            for path, checksum in filesAndHashes:
-                self.assertTrue(os.path.isfile(path),
-                                msg="check whether '{path}' was extracted "
-                                    "correctly.".format(path=path))
-                with open(path, 'rb') as f:
-                    self.assertEqual(hashlib.sha256(f.read()).hexdigest(), checksum)
-
-
-if __name__ == "__main__":
-    os.chdir(os.path.dirname(__file__))
-
-    import argparse
-
-    parser = argparse.ArgumentParser()
-    parser.add_argument(
-        "-v",
-        "--verbose",
-        action="store_true",
-        default=False,
-        help="Spew out even more information than normal",
-    )
-    common.options = common.parse_args(parser)
-
-    newSuite = unittest.TestSuite()
-    newSuite.addTest(unittest.makeSuite(SignaturesTest))
-    unittest.main(failfast=False)