Add env variable to suppress the notice about deprecated SVN

Also removed part of the message that encourages users to disable updates to
depot_tools. If the users do not enable updates, it prevents landing changes into
project repositories that depend on having latest version of the depot_tools, e.g.
https://codereview.chromium.org/1152823005/.

R=akuegel@chromium.org
TBR=maruel@chromium.org, iannucci@chromium.org
BUG=475320

Review URL: https://codereview.chromium.org/1162153004

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@295486 0039d316-1c4b-4281-b951-d872f2087c98

gclient_scm.py

@@ -1169,16 +1169,13 @@ class SVNWrapper(SCMWrapper):
     'svn support so please switch to git.',
     'Tracking bug: http://crbug.com/475320',
     'Request a new git repository at: ',
-    '  https://code.google.com/p/chromium/issues/entry?template=Infra-Git',
-    '',
-    'If subversion support is needed, pin your depot_tools to ',
-    'c20f470011e2ea4d81527976f3bded2c13e258af and set the env var',
-    'DEPOT_TOOLS_UPDATE=0',
-    'Thank you for your business!')
+    '  https://code.google.com/p/chromium/issues/entry?template=Infra-Git')
 
   def __init__(self, *args, **kwargs):
     super(SVNWrapper, self).__init__(*args, **kwargs)
-    if not SVNWrapper._PRINTED_DEPRECATION:
+    suppress_deprecated_notice = os.environ.get(
+        'SUPPRESS_DEPRECATED_SVN_NOTICE', False)
+    if not SVNWrapper._PRINTED_DEPRECATION and not suppress_deprecated_notice:
       SVNWrapper._PRINTED_DEPRECATION = True
       sys.stderr.write('\n'.join(self._MESSAGE) + '\n')