add function for checking entra group exists, remove try except

data_safe_haven/external/api/graph_api.py

@@ -140,7 +140,11 @@ def add_user_to_group(
         """
         try:
             user_id = self.get_id_from_username(username)
-            group_id = self.get_id_from_groupname(group_name)
+            if self.entra_group_exists(group_name):
+                group_id = self.get_id_from_groupname(group_name)
+            else:
+                msg = f"Group '{group_name}' not found."
+                raise DataSafeHavenMicrosoftGraphError(msg)
             json_response = self.http_get(
                 f"{self.base_endpoint}/groups/{group_id}/members",
             ).json()
@@ -321,7 +325,7 @@ def create_group(self, group_name: str) -> None:
             DataSafeHavenMicrosoftGraphError if the group could not be created
         """
         try:
-            if self.get_id_from_groupname(group_name):
+            if self.entra_group_exists(group_name):
                 self.logger.info(
                     f"Found existing Entra group '[green]{group_name}[/]'.",
                 )
@@ -515,18 +519,17 @@ def get_service_principal_by_name(
         except (DataSafeHavenMicrosoftGraphError, StopIteration):
             return None
 
+    def entra_group_exists(self, group_name: str) -> bool:
+        return bool(any(x["displayName"] == group_name for x in self.read_groups()))
+
     def get_id_from_groupname(self, group_name: str) -> str:
-        try:
-            return str(
-                next(
-                    group
-                    for group in self.read_groups()
-                    if group["displayName"] == group_name
-                )["id"]
-            )
-        except (DataSafeHavenMicrosoftGraphError, StopIteration):
-            msg = "Admin group not found. Check that the group exists and that you have the correct permissions."
-            raise DataSafeHavenMicrosoftGraphError(msg) from None
+        return str(
+            next(
+                group
+                for group in self.read_groups()
+                if group["displayName"] == group_name
+            )["id"]
+        )
 
     def get_id_from_username(self, username: str) -> str | None:
         try:
@@ -1016,6 +1019,9 @@ def remove_user_from_group(
         """
         try:
             user_id = self.get_id_from_username(username)
+            if not self.entra_group_exists(group_name):
+                msg = f"Group '{group_name}' not found."
+                raise DataSafeHavenMicrosoftGraphError(msg)
             group_id = self.get_id_from_groupname(group_name)
             # Check whether user is in group
             json_response = self.http_get(