TypeError on running 'brownie bake token'
_Originally posted by @rattle99 as https://github.com/brownie-mix/token-mix/issues/3..._

```
Ubuntu 18.04.4 LTS
Python 3.6.9
```
Running `brownie bake token` returns error.
```
Brownie v1.9.7 - Python development framework for Ethereum

Downloading from https://github.com/brownie-mix/token-mix/archive/master.zip...
110iB [00:00, 5.47kiB/s]
  File "brownie/_cli/__main__.py", line 56, in main
    importlib.import_module(f"brownie._cli.{cmd}").main()
  File "brownie/_cli/bake.py", line 26, in main
    path = project.from_brownie_mix(args["<mix>"], args["<path>"], args["--force"])
  File "brownie/project/main.py", line 571, in from_brownie_mix
    _stream_download(url, str(project_path.parent))
  File "brownie/project/main.py", line 876, in _stream_download
    content += data
TypeError: can't concat str to bytes
```
diff --git a/brownie/project/main.py b/brownie/project/main.py
index fd6ba759..715055dd 100644
--- a/brownie/project/main.py
+++ b/brownie/project/main.py
@@ -867,6 +867,18 @@ def _load_sources(project_path: Path, subfolder: str, allow_json: bool) -> Dict:
 
 def _stream_download(download_url: str, target_path: str) -> None:
     response = requests.get(download_url, stream=True, headers=REQUEST_HEADERS)
+
+    if response.status_code == 404:
+        raise ConnectionError(
+            f"404 error when attempting to download from {download_url} - "
+            "are you sure this is a valid mix? https://github.com/brownie-mix"
+        )
+    if response.status_code != 200:
+        raise ConnectionError(
+            f"Received status code {response.status_code} when attempting "
+            f"to download from {download_url}"
+        )
+
     total_size = int(response.headers.get("content-length", 0))
     progress_bar = tqdm(total=total_size, unit="iB", unit_scale=True)
     content = bytes()
['brownie/project/main.py']