camo: Clean up type ignores.

Signed-off-by: Anders Kaseorg <anders@zulipchat.com>

zerver/lib/camo.py

@@ -1,5 +1,5 @@
 from django.conf import settings
-import codecs
+import binascii
 import hashlib
 import hmac
 
@@ -7,7 +7,7 @@ def generate_camo_url(url: str) -> str:
     encoded_url = url.encode("utf-8")
     encoded_camo_key = settings.CAMO_KEY.encode("utf-8")
     digest = hmac.new(encoded_camo_key, encoded_url, hashlib.sha1).hexdigest()
-    hex_encoded_url = codecs.encode(encoded_url, "hex")  # type: ignore # https://github.com/python/typeshed/issues/300
+    hex_encoded_url = binascii.b2a_hex(encoded_url)
     return "%s/%s" % (digest, hex_encoded_url.decode("utf-8"))
 
 # Encodes the provided URL using the same algorithm used by the camo

zerver/views/camo.py

@@ -7,7 +7,7 @@ from django.http import (
 from zerver.lib.camo import is_camo_url_valid
 from zerver.lib.thumbnail import generate_thumbnail_url
 
-import codecs
+import binascii
 
 def handle_camo_url(request: HttpRequest, digest: str,
                     received_url: str) -> HttpResponse:
@@ -15,8 +15,8 @@ def handle_camo_url(request: HttpRequest, digest: str,
         return HttpResponseNotFound()
 
     hex_encoded_url = received_url.encode('utf-8')
-    hex_decoded_url = codecs.decode(hex_encoded_url, 'hex')
-    original_url = hex_decoded_url.decode('utf-8')  # type: ignore # https://github.com/python/typeshed/issues/300
+    hex_decoded_url = binascii.a2b_hex(hex_encoded_url)
+    original_url = hex_decoded_url.decode('utf-8')
     if is_camo_url_valid(digest, original_url):
         return redirect(generate_thumbnail_url(original_url, is_camo_url=True))
     else: