Apply pyfmt to fbcode/tools

Summary:
Formats a subset of opted-in Python files in fbsource.
Black formatting was applied first, which is guaranteed
safe as the AST will not have changed during formatting.
Pyfmt was then run, which also includes import sorting.
The changes from isort were manually reviewed, and
some potentially dangerous changes were reverted,
and the `# isort:skip_file` directive was added to those
files. A final run of pyfmt shows no more changes to
be applied.

Reviewed By: zertosh

Differential Revision: D24106756

fbshipit-source-id: 7efa84885ffb5bc664b50ba5d9aba0e9984e455a

xar/deprecated/mount_xar.py

@@ -94,7 +94,9 @@ def _read_header(self):
 
     def mount(self, xarexec):
         logger.info("Mounting %s with %s" % (self.filename, xarexec))
-        proc = subprocess.Popen([xarexec.split(), "-m", self.filename], stdout=subprocess.PIPE)
+        proc = subprocess.Popen(
+            [xarexec.split(), "-m", self.filename], stdout=subprocess.PIPE
+        )
         stdout, _ = proc.communicate()
         if proc.returncode != 0:
             logger.fatal("Mount of %s failed, see stderr for details" % self.filename)