Explicitly detect mime type

newswire.py

@@ -153,7 +153,7 @@ def _downloadNewswireFeedFavicon(session, baseDir: str,
     timeoutSec = 10
     imageData, mimeType = \
         downloadImageAnyMimeType(session, favUrl, timeoutSec, debug)
-    if not imageData:
+    if not imageData or not mimeType:
         return False
     if 'image/png' in mimeType:
         favUrl = favUrl.replace('.ico', '.png')

session.py

@@ -458,7 +458,7 @@ def downloadImage(session, baseDir: str, url: str,
 def downloadImageAnyMimeType(session, url: str, timeoutSec: int, debug: bool):
     """http GET for an image with any mime type
     """
-    mimeType = 'image/png'
+    mimeType = None
     contentType = None
     result = None
     try: