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

dart/tools/build.py

Index: dart/tools/build.py
diff --git a/dart/tools/build.py b/dart/tools/build.py
index f7ad04575bbbd784da0d671346e537bd671ae060..886749f6ef77e868f687e1571867cc989ebdffca 100755
--- a/dart/tools/build.py
+++ b/dart/tools/build.py
@@ -266,9 +266,13 @@ PhaseScriptExecution "Action \"upload_sdk_py\"" xcodebuild/dart.build/...
     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 '):