Make dirty checking in check_gn_headers.py more robust

build/check_gn_headers.py

 #!/usr/bin/env python
 # Copyright 2017 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Find header files missing in GN.
 
 This script gets all the header files from ninja_deps, which is from the true
 dependency generated by the compiler, and report if they don't exist in GN.
 """
@@ skipping 130 matching lines @@
       if i.startswith('src/'):
         i = i[4:]
         prefixes.add(i)
   except Exception as e:
     err = str(e)
   q.put((prefixes, err))
 
 
 def IsBuildClean(out_dir):
   cmd = [os.path.join(DEPOT_TOOLS_DIR, 'ninja'), '-C', out_dir, '-n']
-  out = subprocess.check_output(cmd)
-  return 'no work to do.' in out
-
+  try:
+    out = subprocess.check_output(cmd)
+    return 'no work to do.' in out
+  except Exception as e:
+    print e
+    return False
 
 def ParseWhiteList(whitelist):
   out = set()
   for line in whitelist.split('\n'):
     line = re.sub(r'#.*', '', line).strip()
     if line:
       out.add(line)
   return out
 
 
@@ skipping 128 matching lines @@
     count = {k: len(v) for (k, v) in d.iteritems()}
     for f in sorted(count, key=count.get, reverse=True):
       if f in missing:
         print count[f], f
 
   return 1
 
 
 if __name__ == '__main__':
   sys.exit(main())