allow common.get_apk_id() to be used in the API

If a project uses fdroidserver as a library, then just calls
common.get_apk_id(), it will now work.  Before, that project would have had
to include something like `common.config = {}` to avoid a stacktrace.

fdroidserver/common.py

@@ -2689,9 +2689,11 @@ def get_apk_id(apkfile):
     try:
         return get_apk_id_androguard(apkfile)
     except zipfile.BadZipFile as e:
-        logging.error(apkfile + ': ' + str(e))
-        if 'aapt' in config:
+        if config and 'aapt' in config:
+            logging.error(apkfile + ': ' + str(e))
             return get_apk_id_aapt(apkfile)
+        else:
+            raise e
 
 
 def get_apk_id_androguard(apkfile):

tests/common.TestCase

@@ -21,7 +21,7 @@ import textwrap
 import yaml
 import gzip
 import stat
-from zipfile import ZipFile, ZipInfo
+from zipfile import BadZipFile, ZipFile, ZipInfo
 from unittest import mock
 from pathlib import Path
 
@@ -959,9 +959,24 @@ class CommonTest(unittest.TestCase):
                 self.assertEqual(versionCode, vc, 'aapt versionCode parsing failed for ' + apkfilename)
                 self.assertEqual(versionName, vn, 'aapt versionName parsing failed for ' + apkfilename)
 
+    def test_get_apk_id_bad_path(self):
         with self.assertRaises(FDroidException):
             fdroidserver.common.get_apk_id('nope')
 
+    def test_get_apk_id_api_call(self):
+        self.assertEqual(
+            ('info.guardianproject.urzip', '100', '0.1'),
+            fdroidserver.common.get_apk_id('urzip.apk'),
+        )
+
+    def test_get_apk_id_bad_zip(self):
+        os.chdir(self.tmpdir)
+        badzip = 'badzip.apk'
+        with open(badzip, 'w') as fp:
+            fp.write('not a ZIP')
+        with self.assertRaises(BadZipFile):
+            fdroidserver.common.get_apk_id(badzip)
+
     def test_get_apk_id_aapt_regex(self):
         files = glob.glob(os.path.join(self.basedir, 'build-tools', '[1-9]*.*', '*.txt'))
         self.assertNotEqual(0, len(files))