rebaseline.py: skip any platforms we don't have actual results for, with warning message

tools/rebaseline.py

Index: tools/rebaseline.py
===================================================================
--- tools/rebaseline.py	(revision 10016)
+++ tools/rebaseline.py	(working copy)
@@ -62,8 +62,6 @@
     'Test-Android-Nexus7-Tegra3-Arm7-Release',
    'base-android-nexus-s':
     'Test-Android-NexusS-SGX540-Arm7-Release',
-   'base-android-xoom':
-    'Test-Android-Xoom-Tegra2-Arm7-Release',

[borenet, 2013/07/11 18:11:34]

I'm pretty sure we still want this.  The GMs just aren't getting created because
of the crash/reboot problem going on right now.

[epoger, 2013/07/11 18:16:17]

The problem is, because we have NO actual results for this platform yet,
rebaseline.py crashes:

$ tools/rebaseline.py --expectations-root $EXPECTATIONS_DIR
unable to read URL
http://skia-autogen.googlecode.com/svn/gm-actual/base-android-xoom/Test-Andro...:
HTTP Error 404: Not Found
$ echo $?
1

Which is as we want it... if there is a problem, rebaseline.py should fail.

Removing this platform from the list allows the tool to successfully complete.

In my view, until we actually HAVE actual results available for rebaselining on
this platform, we should remove it from the list.

Do you have a counterproposal that will allow rebaselining of other platforms to
continue?

[borenet, 2013/07/11 18:20:08]

Do we really want it to fail?  My preference would be a warning ("Couldn't find
GM actuals for X"), but ONLY if the user specifically requested that platform. 
Ideally, there shouldn't even be a list here.  We should be able to rebaseline
any *available* platform.  This gets easier if we flatten things out to
"<BuilderName>.json" so that we just have to "svn ls" once and then we know what
platforms are available.

    'base-android-nexus-10':
     'Test-Android-Nexus10-MaliT604-Arm7-Release',
    'base-android-nexus-4':
@@ -108,7 +106,10 @@
     # a path on local storage.
     def _GetFileContents(self, filepath):
         if filepath.startswith('http:') or filepath.startswith('https:'):
-            return urllib2.urlopen(filepath).read()
+            try:
+                return urllib2.urlopen(filepath).read()
+            except urllib2.HTTPError as e:
+                raise Exception('unable to read URL %s: %s' % (filepath, e))

[epoger, 2013/07/11 18:08:30]

while I was at it, improved error reporting so the caller can see which URL
could not be fetched

         else:
             return open(filepath, 'r').read()