Fix crash in Folder, GNU and Crates backends

anitya/lib/backends/crates.py

@@ -149,6 +149,9 @@ def _get_versions(cls, project):
         try:
             req = cls.call_url(url, last_change=last_change)
             req.raise_for_status()
+            # Not modified
+            if req.status_code == 304:
+                return []
             data = req.json()
         except requests.RequestException as e:
             raise AnityaPluginException(

anitya/lib/backends/folder.py

@@ -86,11 +86,11 @@ def get_versions(cls, project):
 
         versions = []
 
-        # Not modified
-        if req.status_code == 304:
-            return versions
-
         if not isinstance(req, six.string_types):
+            # Not modified
+            if req.status_code == 304:
+                return versions
+
             req = req.text
 
         try:

anitya/lib/backends/gnu.py

@@ -11,6 +11,8 @@
 from anitya.lib.backends import BaseBackend, REGEX, get_versions_by_regex_for_text
 from anitya.lib.exceptions import AnityaPluginException
 
+import six
+
 
 DEFAULT_REGEX = 'href="([0-9][0-9.]*)/"'
 
@@ -83,9 +85,10 @@ def get_versions(cls, project):
             )
 
         versions = []
-        # Not modified
-        if req.status_code == 304:
-            return versions
+        if not isinstance(req, six.string_types):
+            # Not modified
+            if req.status_code == 304:
+                return versions
 
         try:
             regex = REGEX % {"name": project.name}

anitya/tests/lib/backends/test_crates.py

@@ -100,6 +100,19 @@ def test__get_versions_no_json(self, mock_call_url):
             crates.CratesBackend._get_versions(project)
             self.assertIn("Failed to decode JSON", str(context_manager.exception))
 
+    def test_get_versions_not_modified(self):
+        """Assert that not modified response is handled correctly"""
+        pid = 1
+        project = models.Project.get(self.session, pid)
+        exp_url = "https://crates.io/api/v1/crates/itoa/versions"
+
+        with mock.patch("anitya.lib.backends.BaseBackend.call_url") as m_call:
+            m_call.return_value = mock.Mock(status_code=304)
+            versions = crates.CratesBackend.get_versions(project)
+
+            m_call.assert_called_with(exp_url, last_change=None)
+            self.assertEqual(versions, [])
+
 
 if __name__ == "__main__":
     unittest.main(verbosity=2)