_utils.py: fix lint and format errors

Author: abderrahim

setup.cfg

@@ -28,7 +28,7 @@ warn_no_return = True
 
 # Ignore missing stubs for third-party packages.
 # In future, these should be re-enabled if/when stubs for them become available.
-[mypy-copyreg,grpc,pluginbase,psutil,pyroaring,ruamel,multiprocessing.forkserver]
+[mypy-copyreg,grpc,pluginbase,psutil,pyroaring,ruamel,multiprocessing.forkserver,cython.*]
 ignore_missing_imports=True
 
 # Ignore issues with generated files and vendored code

src/buildstream/_utils.py

@@ -22,9 +22,9 @@
 This module contains utilities that have been optimized in Cython
 """
 
-import cython
-from cython.cimports.cpython.pystate import PyThreadState_SetAsyncExc
-from cython.cimports.cpython.ref import PyObject
+import cython  # pylint: disable=import-error
+from cython.cimports.cpython.pystate import PyThreadState_SetAsyncExc  # pylint: disable=import-error
+from cython.cimports.cpython.ref import PyObject  # pylint: disable=import-error
 from ._signals import TerminateException
 
 
@@ -37,8 +37,7 @@ def url_directory_name(url: str):
     Returns:
        A string which can be used as a directory name
     """
-    return ''.join([_transl(x) for x in url])
-
+    return "".join([_transl(x) for x in url])
 
 
 # terminate_thread()