gitbook: add automated checking for unused assets, remove unused assets

check_unused_assets.py

@@ -0,0 +1,22 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+import subprocess
+
+EXCLUDE = ('clever4-front-white.png', '.DS_Store', 'travis-instruction-8.png')
+code = 0
+
+os.chdir('./docs')
+
+for root, dirs, files in os.walk('assets'):
+    for f in files:
+        if f not in EXCLUDE:
+            path = os.path.join(root, f)
+            try:
+                subprocess.check_output(['grep', '-F', '-r', path, './ru', './en'])
+            except subprocess.CalledProcessError:
+                print('\x1b[1;31mAssets file {} is not used\x1b[0m'.format(path))
+                code = 1
+
+sys.exit(code)