cros_chroot: Make chroot creating/destruction less verbose

Allow for the creation and the destruction of the chroot to be less
noisy.

Also, speed up entering the chroot when brillo/cros chroot is called.

BUG=brillo:710
TEST=unittests + manual tests

Change-Id: I9413d192b22eeb64fe2f4b912f869e92f170a8ce
Reviewed-on: https://chromium-review.googlesource.com/263742
Reviewed-by: Ralph Nathan <ralphnathan@chromium.org>
Tested-by: Ralph Nathan <ralphnathan@chromium.org>
Commit-Queue: Ralph Nathan <ralphnathan@chromium.org>
Trybot-Ready: Ralph Nathan <ralphnathan@chromium.org>
diff --git a/scripts/cros_sdk.py b/scripts/cros_sdk.py
index eeb1647..a472bfa 100644
--- a/scripts/cros_sdk.py
+++ b/scripts/cros_sdk.py
@@ -84,6 +84,7 @@
   # fail if asked to resume a complete file.
   # pylint: disable=C0301,W0631
   # https://sourceforge.net/tracker/?func=detail&atid=100976&aid=3482927&group_id=976
+  logging.notice('Downloading chroot files.')
   for url in urls:
     # http://www.logilab.org/ticket/8766
     # pylint: disable=E1101
@@ -94,7 +95,7 @@
         return parsed.path
       continue
     content_length = 0
-    print('Attempting download: %s' % url)
+    logging.debug('Attempting download from %s', url)
     result = retry_util.RunCurl(
         ['-I', url], redirect_stdout=True, redirect_stderr=True,
         print_cmd=False)
@@ -134,7 +135,7 @@
     if filename == tarball_name or filename.startswith(ignored_prefix):
       continue
 
-    print('Cleaning up old tarball: %s' % (filename,))
+    logging.info('Cleaning up old tarball: %s' % (filename,))
     osutils.SafeUnlink(os.path.join(storage_dir, filename))
 
   return tarball_dest
@@ -149,6 +150,7 @@
   if nousepkg:
     cmd.append('--nousepkg')
 
+  logging.notice('Creating chroot. This may take a few minutes...')
   try:
     cros_build_lib.RunCommand(cmd, print_cmd=False)
   except cros_build_lib.RunCommandError:
@@ -160,6 +162,7 @@
   cmd = MAKE_CHROOT + ['--chroot', chroot_path,
                        '--delete']
   try:
+    logging.notice('Deleting chroot.')
     cros_build_lib.RunCommand(cmd, print_cmd=False)
   except cros_build_lib.RunCommandError:
     raise SystemExit('Running %r failed!' % cmd)