cosmetic: blacken setup.py

setup.py

@@ -16,6 +16,7 @@ from setuptools.command.sdist import sdist
 
 try:
     from Cython.Build import cythonize
+
     cythonize_import_error_msg = None
 except ImportError as exc:
     # either there is no Cython installed or there is some issue with it.
@@ -85,9 +86,12 @@ else:
 
     cython_c_files = [fn.replace(".pyx", ".c") for fn in cython_sources]
     if not on_rtd and not all(os.path.exists(path) for path in cython_c_files):
-        raise ImportError("The GIT version of Borg needs a working Cython. " +
-                          "Install or fix Cython or use a released borg version. " +
-                          "Importing cythonize failed with: " + cythonize_import_error_msg)
+        raise ImportError(
+            "The GIT version of Borg needs a working Cython. "
+            + "Install or fix Cython or use a released borg version. "
+            + "Importing cythonize failed with: "
+            + cythonize_import_error_msg
+        )
 
 
 cmdclass = {"build_ext": build_ext, "sdist": Sdist}