"fix" incomplete MIME types (#632)

e-/exhentai's original image downloads currently send
incomplete/invalid Content-Type headers, "jpg" instead
of "image/jpg" etc, since the last update.
(https://forums.e-hentai.org/index.php?showtopic=236113)

This change prepends any Content-Type value missing a
media type specification with "image/", transforming it
into a valid MIME type.

(A global solution to a local problem, but it shouldn't
 cause any issues anywhere else)

CHANGELOG.md

@@ -1,5 +1,7 @@
 # Changelog
 
+## Unreleased
+
 ## 1.13.1 - 2020-03-01
 ### Additions
 - [hentaihand] add extractors ([#605](https://github.com/mikf/gallery-dl/issues/605))

gallery_dl/downloader/http.py

@@ -193,6 +193,9 @@ def get_extension(self, response):
         mtype = response.headers.get("Content-Type", "image/jpeg")
         mtype = mtype.partition(";")[0]
 
+        if "/" not in mtype:
+            mtype = "image/" + mtype
+
         if mtype in MIMETYPE_MAP:
             return MIMETYPE_MAP[mtype]
 

gallery_dl/version.py

@@ -6,4 +6,4 @@
 # it under the terms of the GNU General Public License version 2 as
 # published by the Free Software Foundation.
 
-__version__ = "1.13.1"
+__version__ = "1.13.2-dev"