models/Observation: Improve requests exception handling (W0703)

Fixes a broad-except (W0703) pylint error.

Signed-off-by: Fabian P. Schmidt <kerel@mailbox.org>

network/base/models.py

@@ -515,9 +515,11 @@ class Observation(models.Model):
             if self.archive_url:
                 try:
                     request = requests.get(self.archive_url, allow_redirects=False)
+                    request.raise_for_status()
+
                     url = request.headers['Location']
                     return url
-                except Exception as error:
+                except requests.exceptions.RequestException as error:
                     logger = logging.getLogger(__name__)
                     logger.warning("Error in request to '%s'. Error: %s", self.archive_url, error)
                     return ''