Catch CalledProcessError which is throw if the command has non-zero exit code.

dart/tools/build.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 #
 
 import optparse
 import os
 import shutil
@@ skipping 248 matching lines @@
 
   section = None
   chunk = []
   # Is stdout a terminal which supports colors?
   is_fancy_tty = False
   clr_eol = None
   if sys.stdout.isatty():
     term = os.getenv('TERM', 'dumb')
     # The capability "clr_eol" means clear the line from cursor to end
     # of line.  See man pages for tput and terminfo.
-    clr_eol = subprocess.check_output(['tput', '-T' + term, 'el'])
-    if clr_eol:
-      is_fancy_tty = True
+    try:
+      clr_eol = subprocess.check_output(['tput', '-T' + term, 'el'],
+                                        stderr=subprocess.STDOUT)

[kustermann, 2013/04/06 14:31:05]

I don't understand why you added 'stderr=subprocess.STDOUT'.
If tput outputs something to stderr than we set 'is_fancy_tty = True' -- I don't
think this is what we want.

[ahe, 2013/04/08 12:46:29]

tput is a well-behaved Unix command.  It doesn't print to stderr unless the
return code is non-zero.

But I could probably do something like this:

with open('/dev/null', 'a') as dev_null:
  ... stderr=dev_null

+      if clr_eol:
+        is_fancy_tty = True
+    except subprocess.CalledProcessError:
+      is_fancy_tty = False
   for line in unbuffered(process.stdout.readline):
     line = line.rstrip()
     if line.startswith('=== BUILD ') or line.startswith('** BUILD '):
       if not is_empty_chunk(chunk):
         print '\n'.join(chunk)
       section = line
       if is_fancy_tty:
         # If stdout is a terminal, emit "progress" information.  The
         # progress information is the first line of the current chunk.
         # After printing the line, move the cursor back to the
@@ skipping 120 matching lines @@
         process.wait()
         if process.returncode != 0:
           print "BUILD FAILED"
           return 1
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main())