Issue 27948: Allow backslashes in the literal string portion of f-strings, but not in the expressions. Also, require expressions to begin and end with literal curly braces.

Lib/http/client.py

@@ -1060,7 +1060,7 @@ class HTTPConnection:
 
                 if encode_chunked and self._http_vsn == 11:
                     # chunked encoding
-                    chunk = f'{len(chunk):X}''\r\n'.encode('ascii') + chunk \
+                    chunk = f'{len(chunk):X}\r\n'.encode('ascii') + chunk \
                         + b'\r\n'
                 self.send(chunk)