Merge pull request #6982 from smamessier/fix_non_ascii_error

Fixed non-ascii error when using COMPOSE_DOCKER_CLI_BUILD=1 for Buildkit

compose/service.py

@@ -1806,6 +1806,9 @@ class _CLIBuilder(object):
                 line = p.stdout.readline()
                 if not line:
                     break
+                # Fix non ascii chars on Python2. To remove when #6890 is complete.
+                if six.PY2:
+                    magic_word = str(magic_word)
                 if line.startswith(magic_word):
                     appear = True
                 yield json.dumps({"stream": line})