tools/dbus_exporter: deblackify and shorten code a bit

When we do mkdir, we should just use 0o777 and let the umask take care of the
rest. Specifying an explicit mode is inappropriate. And when touching the code,
let's replace black madness with normal python style.

tools/dbus_exporter.py

@@ -4,58 +4,39 @@ from argparse import ArgumentParser
 from pathlib import Path
 from subprocess import run, PIPE
 
-
 def extract_interfaces_xml(output_dir, executable):
-    list_interfaces_process = run(
+    proc = run(
         args=[executable.absolute(), '--bus-introspect', 'list'],
         stdout=PIPE,
         check=True,
-        universal_newlines=True,
-    )
+        universal_newlines=True)
 
-    interfaces_lines = list_interfaces_process.stdout.splitlines()
-
-    interface_names = [x.split()[1] for x in interfaces_lines]
+    interface_names = (x.split()[1] for x in proc.stdout.splitlines())
 
     for interface_name in interface_names:
-        interface_introspection_run = run(
+        proc = run(
             args=[executable.absolute(), '--bus-introspect', interface_name],
             stdout=PIPE,
             check=True,
-            universal_newlines=True,
-        )
+            universal_newlines=True)
 
         interface_file_name = output_dir / (interface_name + '.xml')
-        with open(interface_file_name, mode='w') as f:
-            f.write(interface_introspection_run.stdout)
+        interface_file_name.write_text(proc.stdout)
         interface_file_name.chmod(0o644)
 
-
-def iterate_executables(output_dir, executables):
-    output_dir.mkdir(mode=0o755, exist_ok=True)
-
-    for exe in executables:
-        extract_interfaces_xml(output_dir, exe)
-
-
 def main():
     parser = ArgumentParser()
-
-    parser.add_argument(
-        'output',
-        type=Path,
-    )
-
-    parser.add_argument(
-        'executables',
-        type=Path,
-        nargs='+',
-    )
+    parser.add_argument('output',
+                        type=Path)
+    parser.add_argument('executables',
+                        nargs='+',
+                        type=Path)
 
     args = parser.parse_args()
 
-    iterate_executables(args.output, args.executables)
-
+    args.output.mkdir(exist_ok=True)
+    for exe in args.executables:
+        extract_interfaces_xml(args.output, exe)
 
 if __name__ == '__main__':
     main()