Add test for testing datadir not in sdist

tests/test_install.py

@@ -1,5 +1,7 @@
 from pathlib import Path
 from subprocess import check_output
+from tarfile import TarInfo
+from tarfile import open as tar_open
 from unittest.case import TestCase
 
 try:
@@ -26,3 +28,11 @@ class InstallTest(TestCase):
         self.assertTrue(
             expr=Path(etag_path).exists(),
             msg=f'{etag_path!r} doesn\'t exist.')
+
+    def test_sdist_excludes_datadir(self):
+        'The created sdist should not contain the data dir.'
+        latest_sdist = list(Path('dist').glob(pattern='*.tar.gz'))[-1]
+        tar_file = tar_open(name=latest_sdist, mode='r:gz')
+        for tarinfo in tar_file:  # type: TarInfo
+            self.assertNotIn(
+                member='/validate_email/data/', container=tarinfo.name)

validate_email/updater.py

@@ -119,7 +119,7 @@ class BlacklistUpdater(object):
         except HTTPError as exc:
             if exc.code == 304:
                 # Not modified, update date on the tmp file
-                LOGGER.debug(msg=f'Local file is fresh enough (same ETag).')
+                LOGGER.debug(msg='Local file is fresh enough (same ETag).')
                 BLACKLIST_FILEPATH_TMP.touch()
                 return
             raise