pr feedback: explain edge cases in more detail

zappa/handler.py

@@ -583,12 +583,16 @@ def handler(self, event, context):
                         )
 
                     if response.data:
+                        # We base64 encode for two reasons when BINARY_SUPPORT is enabled:
+                        # - Content-Encoding is present, which is commonly used by compression mechanisms to indicate
+                        #   that the content is in br/gzip/deflate/etc encoding
+                        #   (Related: https://github.com/zappa/Zappa/issues/908). Content like this must be
+                        #   transmitted as b64.
+                        # - The response is assumed to be some binary format (since BINARY_SUPPORT is enabled and it
+                        #   isn't application/json or text/)
                         if settings.BINARY_SUPPORT and response.headers.get(
                             "Content-Encoding"
                         ):
-                            # We could have a text response that's gzip
-                            # encoded. Therefore, we base-64 encode it.
-                            # Related: https://github.com/zappa/Zappa/issues/908
                             zappa_returndict["body"] = base64.b64encode(
                                 response.data
                             ).decode("utf-8")