Refactor create_repo (#84)

* Refactor create_repo

* Improve code quality

Author: SBrandeis

src/huggingface_hub/hf_api.py

@@ -306,17 +306,20 @@ def create_repo(
             headers={"authorization": "Bearer {}".format(token)},
             json=json,
         )
-        if exist_ok and r.status_code == 409:
-            d = r.json()
-            return d["url"]
 
         try:
             r.raise_for_status()
-        except HTTPError as e:
-            if r.json():
-                if "error" in r.json():
-                    raise HTTPError("{} - {}".format(e, r.json()["error"]))
-            raise e
+        except HTTPError as err:
+            if not (exist_ok and err.response.status_code == 409):
+                try:
+                    additional_info = r.json().get("error", None)
+                    if additional_info:
+                        new_err = f"{err.args[0]} - {additional_info}"
+                        err.args = (new_err,) + err.args[1:]
+                except ValueError:
+                    pass
+
+                raise err
 
         d = r.json()
         return d["url"]