py: Reformat all Python files consistently

This commit is the unmodified results of running
```
black $(git ls-files '*.py')
```
with black version 19.10b0. See #2046.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

docs/reference/gio/concat-files-helper.py

@@ -21,10 +21,14 @@
 import sys
 
 if len(sys.argv) < 3:
-  print('Usage: {} <output file> <input file 1> ...'.format(os.path.basename(sys.argv[0])))
-  sys.exit(1)
+    print(
+        "Usage: {} <output file> <input file 1> ...".format(
+            os.path.basename(sys.argv[0])
+        )
+    )
+    sys.exit(1)
 
-with open(sys.argv[1], 'w') as outfile:
+with open(sys.argv[1], "w") as outfile:
     for fname in sys.argv[2:]:
         with open(fname) as infile:
             for line in infile: