Fix GraphQL error handling: centralise in request_github_graphql

GraphQL errors come back as HTTP 200 with an "errors" key, bypassing the
status code check. Added a check in request_github_graphql so all callers
get consistent error handling, and removed the now-redundant ad-hoc check
in licences.py.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: rwood-97

src/github_analyser/licences.py

@@ -39,11 +39,6 @@ def get_licence(
     query = _get_licence_query(org_name, repo_name)
 
     response = request_github_graphql({"query": query})
-    # extract repo id from the first response
-    if "errors" in response:
-        print(f"Failed to get licence data for {repo_name}: {response['errors']}")
-        return pd.Series()
-
     repo_id = response["data"]["repository"]["id"]
     repo_url = response["data"]["repository"]["url"]
     licence_info = response["data"]["repository"]["licenseInfo"]

src/github_analyser/utils.py

@@ -76,7 +76,11 @@ def request_github_graphql(payload: Any, headers: Any | None = None) -> Any:
     if response.status_code != 200:
         msg = f"GitHub query failed by code {response.status_code}."
         raise Exception(msg)
-    return response.json()
+    data = response.json()
+    if "errors" in data:
+        msg = f"GitHub GraphQL query returned errors: {data['errors']}"
+        raise Exception(msg)
+    return data
 
 
 def query_with_pagination(