Remove unnecessary HEAD calls in requests downloader

HEAD requests were made to sum a total file size of the download operation. However, the downloader is may be used on URLs where the content is not segmented media. Therefore, the server may not support or respond with the Content-Length header which causes the requests downloader to crash before it even gets a chance to begin downloading.

Even still, this total size value isn't really necessary, and would cause possibly 100s of HEAD requests (in quick succession of each other) on segmented sources. It would also add up-front delay before it actually starts to download.

devine/core/downloaders/requests.py

@@ -48,13 +48,8 @@ def requests(
     if proxy:
         session.proxies.update({"all": proxy})
 
-    total_size = sum(
-        int(session.head(url).headers["Content-Length"])
-        for url, _ in uri
-    )
-
     if progress:
-        progress(total=total_size)
+        progress(total=len(uri))
 
     download_sizes = []
     last_speed_refresh = time.time()
@@ -70,7 +65,7 @@ def requests(
                 f.write(chunk)
                 written += download_size
                 if progress:
-                    progress(advance=download_size)
+                    progress(advance=1)
 
                     now = time.time()
                     time_since = now - last_speed_refresh