feat: Warn about br handling if brotlipy is not installed scrapy#4697

scrapy/downloadermiddlewares/httpcompression.py

@@ -1,5 +1,7 @@
 import io
 import zlib
+import logging
+logger = logging.getLogger(__name__)
 
 from scrapy.utils.gz import gunzip
 from scrapy.http import Response, TextResponse
@@ -13,6 +15,8 @@
     import brotli
     ACCEPTED_ENCODINGS.append(b'br')
 except ImportError:
+    msg = ("brotli is not installed")
+    logger.warning(msg)
     pass
 
 try:
@@ -72,8 +76,11 @@ def _decode(self, body, encoding):
                 # http://www.port80software.com/200ok/archive/2005/10/31/868.aspx
                 # http://www.gzip.org/zlib/zlib_faq.html#faq38
                 body = zlib.decompress(body, -15)
-        if encoding == b'br' and b'br' in ACCEPTED_ENCODINGS:
-            body = brotli.decompress(body)
+        if encoding == b'br':
+            if b'br' in ACCEPTED_ENCODINGS:
+                body = brotli.decompress(body)
+            else: 
+                raise ImportError('brotlipy is not installed')
         if encoding == b'zstd' and b'zstd' in ACCEPTED_ENCODINGS:
             # Using its streaming API since its simple API could handle only cases
             # where there is content size data embedded in the frame