Retry failed downloads.

tests/download-test-images.py

@@ -1,7 +1,6 @@
 import os
 import shutil
 import sys
-import time
 
 from urllib.parse import urlparse
 from zipfile import ZipFile
@@ -88,11 +87,14 @@ def download_dftt_images():
     for url in dftt_urls:
         download(url)
 
-    time.sleep(15)
-
     for filename in os.listdir("."):
         _, ext = os.path.splitext(filename)
         if ext == ".zip":
+            while os.path.getsize(filename) == 154:
+                for url in dftt_urls:
+                    if filename in url:
+                        print(f"Retrying download of {filename}")
+                        download(url)
             print(f"unzipping: {filename}")
             unzip(filename)