Cover auth request error case when requests request fails in HTTPX auth flow

Author: jonathanedey

firebase_admin/_http_client.py

@@ -335,6 +335,7 @@ class call this method to send HTTP requests out. Refer to
 
         Raises:
             HTTPError: Any HTTPX exceptions encountered while making the HTTP call.
+            RequestException: Any requests exceptions encountered while making the HTTP call.
         """
         if 'timeout' not in kwargs:
             kwargs['timeout'] = self.timeout

firebase_admin/messaging.py

@@ -533,13 +533,11 @@ async def send_data(data):
                     url=self._fcm_url,
                     headers=self._fcm_headers,
                     json=data)
-                # HTTP/2 check
-                if resp.http_version != 'HTTP/2':
-                    raise Exception('This messages was not sent with HTTP/2')
-                resp.raise_for_status()
-            # except httpx.HTTPStatusError as exception:
             except httpx.HTTPError as exception:
                 return SendResponse(resp=None, exception=self._handle_fcm_httpx_error(exception))
+            # Catch errors caused by the requests library during authorization
+            except requests.exceptions.RequestException as exception:
+                return SendResponse(resp=None, exception=self._handle_fcm_error(exception))
             else:
                 return SendResponse(resp.json(), exception=None)