Check Django block tags in check-templates.

(imported from commit a5d6336eeba63df365d3e59dce4d7f32aae637c7)

tools/check-templates

@@ -99,11 +99,38 @@ def validate(fn, check_indent=True):
             advance(len(s))
             continue
 
+        # Django tags
+        if looking_at("{% ") and not looking_at("{% end"):
+            s = get_django_tag(text, state.i)
+            tag = s[3:-2].split()[0]
+            if is_django_block_tag(tag):
+                start_tag_matcher(s, tag)
+            advance(len(s))
+            continue
+
+        if looking_at("{% end"):
+            s = get_django_tag(text, state.i)
+            end_tag = s[6:-3]
+            state.matcher(end_tag)
+            advance(len(s))
+            continue
+
         advance(1)
 
     if state.depth != 0:
         return state.matcher("(NO TAG)")
 
+def is_django_block_tag(tag):
+    return tag in [
+        'autoescape',
+        'block',
+        'comment',
+        'for',
+        'if',
+        'ifequal',
+        'verbatim',
+    ]
+
 def get_handlebars_tag(text, i):
     end = i + 2
     while end < len(text) -1 and text[end] != '}':
@@ -113,6 +140,15 @@ def get_handlebars_tag(text, i):
     s = text[i:end+2]
     return s
 
+def get_django_tag(text, i):
+    end = i + 2
+    while end < len(text) -1 and text[end] != '%':
+        end += 1
+    if text[end] != '%' or text[end+1] != '}':
+        raise Exception('Tag missing %}')
+    s = text[i:end+2]
+    return s
+
 def get_html_tag(text, i):
     end = i + 1
     while end < len(text) and text[end] != '>':