Added default value for the quiet parameter

The activate_end method is used in infra/bootstrap/, which doesn't
pass the value for this parameter.

Review URL:

git-svn-id: svn:// 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/bootstrap/ b/bootstrap/
index 5ac12e7..eb596af 100755
--- a/bootstrap/
+++ b/bootstrap/
@@ -154,7 +154,7 @@
          os.path.join(ROOT, '.wheelcache'), '-f', ipath] + requirements)
-def activate_env(env, deps, quiet):
+def activate_env(env, deps, quiet=False):
   if hasattr(sys, 'real_prefix'):
     LOGGER.error('Already activated environment!')