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..4d81ab9f3bacfe482bba969ceb7868a958aeeb94 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
 
@@ -26,6 +27,18 @@ arch_to_pkgarch = {
 pkgarch_to_arch = {v:k for k, v in arch_to_pkgarch.items()}
 
 verbose = False
+color_mode = 'auto'
+
+def Color(message, color):
+  if Color.enabled:
+    return termcolor.colored(message, color)
+  else:
+    return message
+
+
+def CheckStdoutForColorSupport():
+  if color_mode == 'auto':
+    Color.enabled = sys.stdout.isatty()
 
 
 def Memoize(f):
@@ -56,6 +69,20 @@ def Log(message):
   sys.stdout.flush()
 
 
+def LogHeading(message, suffix=''):
+  """Log a colored/highlighted message with optional suffix."""
+  if Color.enabled:
+    Log(Color(message, 'green') + suffix)
+  else:
+    if verbose:
+      # When running in verbose mode make sure heading standout
+      Log('###################################################################')
+      Log(message + suffix)
+      Log('###################################################################')
+    else:
+      Log(message + suffix)
+
+
 def Warn(message):
   Log('warning: ' + message)
 
@@ -244,7 +271,6 @@ 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
 
 
@@ -351,3 +377,6 @@ class InstallLock(Lock):
   def __init__(self, config):
     root = GetInstallRoot(config)
     super(InstallLock, self).__init__(root)
+
+
+CheckStdoutForColorSupport()