do not try to render non-image files with chafa to avoid errors

CHANGELOG

@@ -4,6 +4,7 @@
 - Making python-readability optional
 - Removing "next" and "previous" which are quite confusing and not obvious
 - Fixing a crash when accessing an empty html page
+- Not trying to display non-image files to avoid errors. (this requires "file")
 
 ## 1.3 - April 2th 2022
 - Removed dependency to python-magic. File is now used directly (and should be on every system).

README.md

@@ -78,9 +78,9 @@ To avoid using unstable or too recent libraries, the rule of thumb is that a lib
 
 Run command `version` in offpunk to see if you are missing some dependencies.
 
-Highly recommended (packagers should probably make those mandatory):
+Mandatory or highly recommended (packagers should probably make those mandatory):
 * [less](http://www.greenwoodsoftware.com/less/): mandatory but is probably already on your system
-* [file](https://www.darwinsys.com/file/) is used to get the MIME type of cached objects. Should already be on your system.
+* [file](https://www.darwinsys.com/file/) is used to get the MIME type of cached objects. Should already be on your system and may become mandatory.
 * [xdg-utils](https://www.freedesktop.org/wiki/Software/xdg-utils/) provides xdg-open which is highly recommended to open files without a renderer or a handler. It is also used for mailto: command.
 * The [cryptography library](https://pypi.org/project/cryptography/) will provide a better and slightly more secure experience when using the default TOFU certificate validation mode and is highly recommended (apt-get install python3-cryptography).
 

offpunk.py

@@ -105,6 +105,11 @@ def inline_image(img_file,width):
     #Chafa is faster than timg inline. Let use that one by default
     inline = None
     ansi_img = ""
+    #We avoid errors by not trying to render non-image files
+    if shutil.which("file"):
+        mime = run("file -b --mime-type \"%s\""%img_file).strip()
+        if not "image" in mime:
+            return ansi_img
     if _HAS_CHAFA:
         if _HAS_PIL and not _NEW_CHAFA:
             # this code is a hack to remove frames from animated gif