GetRepositoryFile tool masks GitLab API errors with generic KeyError message

Problem

The GetRepositoryFile tool in duo_workflow_service/tools/repository_files.py does not properly surface GitLab API errors. When the GitLab API returns an error response (e.g., {"message":"404 File Not Found"}), the tool masks this with a generic {"error": "'content'"} message instead.

Root Cause

In GetRepositoryFile._arun() at line 108:

content = base64.b64decode(json.loads(response)["content"]).decode("utf-8")

When GitLab API returns an error response like {"message":"404 File Not Found"}, the code attempts to access the "content" key which doesn't exist in error responses. This raises a KeyError: 'content' that gets caught by the generic exception handler, resulting in {"error": "'content'"} instead of the actual API error.

Expected Behavior

When GitLab API returns:

{"message":"404 File Not Found"}

The tool should surface this error message to the user, not mask it with a generic KeyError.

Current Behavior

API call: curl -X GET -H "Authorization: Bearer $GITLAB_API_PRIVATE_TOKEN" "https://gitlab.com/api/v4/projects/39903947/repository/files/.gitlab%2Fduo%2Fmr-review-instructions.yaml?ref=HEAD"

Returns: {"message":"404 File Not Found"}

But tool execution trace shows: {"error": "'content'"}

Proposed Solution

The code should check for error responses before attempting to access the "content" key:

try:
    response_data = json.loads(response)
    
    # Check if response contains an error message
    if "message" in response_data and "content" not in response_data:
        return json.dumps({"error": response_data["message"]})
    
    if "content" not in response_data:
        return json.dumps({"error": "Missing content in response"})
        
    content = base64.b64decode(response_data["content"]).decode("utf-8")
    return json.dumps({"content": content})
except Exception as e:
    return json.dumps({"error": str(e)})

Impact

This issue affects error visibility and debugging when files don't exist or there are permission issues, making it harder for users to understand what went wrong.