Add a py script to check for bad string formats

Lint finds these, but it's very slow and currently we're not taking lint
errors as fatal. So for now this script will be useful, as nearly every
time I pull from weblate there are at least a couple of these.

F-Droid/tools/check-string-format.py

@@ -0,0 +1,37 @@
+#!/usr/bin/env python2
+
+# Remove extra translations
+
+import glob
+import os
+import sys
+import re
+from xml.etree import ElementTree
+
+formatRe = re.compile(r'(%%|%[^%](\$.)?)')
+
+validFormatRe = re.compile(r'^(%%|%[sd]|%[0-9]\$[sd])$')
+
+count = 0
+
+for d in glob.glob(os.path.join('res', 'values-*')):
+
+    str_path = os.path.join(d, 'strings.xml')
+    if not os.path.exists(str_path):
+        continue
+
+    tree = ElementTree.parse(str_path)
+    root = tree.getroot()
+
+    for e in root.findall('.//string'):
+        for m in formatRe.finditer(e.text):
+            s = m.group(0)
+            if validFormatRe.match(s):
+                continue
+            count += 1
+            print('%s: Invalid format "%s" in "%s"' % (str_path, s, e.text))
+
+if count > 0:
+    print("%d misformatted strings found!" % count)
+    sys.exit(1)
+