Fix error message for unrecognised TLS version

Signed-off-by: Aanand Prasad <aanand.prasad@gmail.com>

compose/cli/command.py

@@ -65,8 +65,9 @@ def get_tls_version(environment):
     tls_attr_name = "PROTOCOL_{}".format(compose_tls_version)
     if not hasattr(ssl, tls_attr_name):
         log.warn(
-            'The {} protocol is unavailable. You may need to update your '
+            'The "{}" protocol is unavailable. You may need to update your '
             'version of Python or OpenSSL. Falling back to TLSv1 (default).'
+            .format(compose_tls_version)
         )
         return None