Add fake stat stub for macOS workaround

This is an attempt to work around the BSD/GNU `stat` incompatibility
for the two calls during storage tests.

$ ./test/bin/stat -c %U /Users/GitHub
GitHub
$ ./test/bin/stat -c %U ./data
ryan
$ ./test/bin/stat -f '%Su' ./data
ryan

Author: mckern

test/bin/stat

@@ -0,0 +1,20 @@
+#!/usr/bin/env python3
+
+# this is an unbelievably narrowly constrained used case:
+# there's a single use of `stat` in this codebase:
+# calling `stat -c %U` to find the username that owns
+# a given path.
+# But this fails on macOS because macOS uses BSD stat,
+# not GNU stat. This very, VERY basic, very brittle
+# wrapper is just to work around this one specific
+# call to stat.
+
+import sys
+from os import stat
+from pwd import getpwuid
+
+def find_owner(filename):
+    return getpwuid(stat(filename).st_uid).pw_name
+
+
+print(find_owner(sys.argv[-1]))