Allow concurrent call to url_download

When two pytest instances run in parallel and download the same ISO using
'url_download', the resulting file ends up corrupted. This commit uses
'tempfile.NamedTemporaryFile' to avoid writing to the same file.

The new implementation also remove the temporary .part file if the
download fails.

Signed-off-by: Vincent Michel <vincent.michel@vates.tech>

Author: vxgmichel

lib/common.py

@@ -10,11 +10,13 @@
 import random
 import string
 import sys
+import tempfile
 import time
 import traceback
 from datetime import datetime
 from enum import Enum
 from functools import lru_cache
+from pathlib import Path
 from uuid import UUID
 
 import requests
@@ -317,13 +319,30 @@ def strtobool(val: str | None) -> bool:
     raise ValueError("invalid truth value '{}'".format(val))
 
 def url_download(url: str, filename: str) -> None:
-    r = requests.get(url, stream=True)
-    r.raise_for_status()
-    tempfilename = filename + ".part"
-    with open(tempfilename, 'wb') as fd:
-        for chunk in r.iter_content(chunk_size=128):
-            fd.write(chunk)
-    os.rename(tempfilename, filename)
+    """
+    Download the content of `url` to the `filename` destination.
+
+    A randomized filename is used during download to prevent file corruption on
+    concurrent use. If the download fails then the temporary file is removed.
+    """
+    destination = Path(filename)
+    destination.parent.mkdir(parents=True, exist_ok=True)
+    with requests.get(url, stream=True) as r:
+        r.raise_for_status()
+        temp_name: str | None = None
+        try:
+            with tempfile.NamedTemporaryFile(
+                dir=destination.parent, prefix=f"{destination.name}.", suffix=".part", delete=False
+            ) as fd:
+                temp_name = fd.name
+                for chunk in r.iter_content(chunk_size=128):
+                    fd.write(chunk)
+        except BaseException:
+            if temp_name is not None:
+                os.unlink(temp_name)
+            raise
+        else:
+            os.rename(temp_name, filename)
 
 def randid(length: int = 6) -> str:
     """