Add initial support for color output in the build system

lib/naclports/util.py

Index: lib/naclports/util.py
diff --git a/lib/naclports/util.py b/lib/naclports/util.py
index 0aae54584175aa067d3c6259be940b546126c615..6573b75693b88aeb2297ff3dddcddfacecc18201 100644
--- a/lib/naclports/util.py
+++ b/lib/naclports/util.py
@@ -8,6 +8,7 @@ import os
 import shutil
 import subprocess
 import sys
+import termcolor
 
 from naclports import error, paths
 
@@ -28,6 +29,18 @@ pkgarch_to_arch = {v:k for k, v in arch_to_pkgarch.items()}
 verbose = False
 
 
+def Color(message, color):
+  if Color.enabled:
+    return termcolor.colored(message, color)
+  else:
+    return message
+
+
+def CheckForColorSupport():
+  Color.enabled = sys.stdout.isatty()

[binji, 2015/01/09 18:24:59]

Is there a better check here? Not all ttys support color, right?

[Sam Clegg, 2015/01/09 22:14:54]

This is the same change that "ls --color=auto" does.

This is from the stackoverflow discussion that seems to back this up:
http://unix.stackexchange.com/questions/9957/how-to-check-if-bash-can-print-c...
"Terminals that don't support ANSI color-changing sequences are rare enough that
it's acceptable to make their users override the default choice. In any case,
make sure your application has an option to force colors on or off."

So, I think as long as I add an option for force it to be disabled we should be
fine.

+CheckForColorSupport()
+
+
 def Memoize(f):
   """Memoization decorator for functions taking one or more arguments."""
   class Memo(dict):
@@ -56,6 +69,16 @@ def Log(message):
   sys.stdout.flush()
 
 
+def LogHeading(message, suffix=''):
+  """Log a colored message with optional suffix."""
+  if Color.enabled:
+    Log(Color(message, 'green') + suffix)
+  else:
+    Log('#####################################################################')
+    Log(message + suffix)
+    Log('#####################################################################')
+
+
 def Warn(message):
   Log('warning: ' + message)
 
@@ -244,7 +267,6 @@ def IsInstalled(package_name, config, stamp_content=None):
   """Returns True if the given package is installed."""
   stamp = GetInstallStamp(package_name, config)
   result = CheckStamp(stamp, stamp_content)
-  Trace("IsInstalled: %s -> %s" % (package_name, result))
   return result