inject_misc_tags no longer fails if document has no head. Resolves #16.

src/caterpillar.py

 #!/usr/bin/env python2
 # -*- coding: utf-8 -*-
 
 # Copyright 2015 Google Inc. All Rights Reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
@@ skipping 268 matching lines @@
   """
   Injects meta and link tags into an HTML document.
 
   Args:
     soup: BeautifulSoup HTML document. Will be modified.
     ca_manifest: Manifest dictionary of _Chrome App_.
     root_path: Path to the root directory of the web app from this HTML file.
       This can be either absolute or relative.
     html_path: Path to the HTML document being modified.
   """
+  head = soup.head
+  if not head:
+    head = soup.new_tag('head')
+    if soup.html:
+      soup.html.insert(0, head)
+    else:
+      soup.insert(0, head)
+
   # Add manifest link tag.
   manifest_path = os.path.join(root_path, PWA_MANIFEST_FILENAME)
   manifest_link = soup.new_tag('link', rel='manifest', href=manifest_path)
-  soup.head.append(manifest_link)
+  head.append(manifest_link)
 
   # Add meta tags (if they don't already exist).
   for tag in ('description', 'author', 'name'):
     if tag in ca_manifest and not soup('meta', {'name': tag}):
       meta = soup.new_tag('meta', content=ca_manifest[tag])
       meta['name'] = tag
-      soup.head.append(meta)
+      head.append(meta)
       logging.debug('Injected `%s` tag into `%s` with content `%s`.', tag,
                     html_path, ca_manifest[tag])
   if not soup('meta', {'charset': True}):
     meta_charset = soup.new_tag('meta', charset='utf-8')
-    soup.head.insert(0, meta_charset)
+    head.insert(0, meta_charset)
 
 
 def insert_todos_into_file(js_path):
   """Inserts TODO comments in a JavaScript file.
 
   The TODO comments inserted should draw attention to places in the converted
   app that the developer will need to edit to finish converting their app.
 
   Args:
     js_path: Path to JavaScript file.
@@ skipping 433 matching lines @@
   if args.mode == 'config':
     configuration.generate_and_save(args.output, args.interactive)
 
   elif args.mode == 'convert':
     config = configuration.load(args.config)
     convert_app(args.input, args.output, config, args.force)
 
 
 if __name__ == '__main__':
   sys.exit(main())