Fix cleanup so we don't have to clobber as much when failures occur

Change-Id: I120c49a38d2a17a2216296a68378fee7345f616a

TBR=petkov

Review URL: http://codereview.chromium.org/3255004

bin/cbuildbot.py

@@ -216,6 +216,7 @@ def _FullCheckout(buildroot, rw_checkout=True, retries=_DEFAULT_RETRIES):
 def _IncrementalCheckout(buildroot, rw_checkout=True,
                          retries=_DEFAULT_RETRIES):
   """Performs a checkout without clobbering previous checkout."""
+  _UprevCleanup(buildroot, error_ok=True)
   RepoSync(buildroot, rw_checkout, retries)
 
 
@@ -281,12 +282,12 @@ def _UprevPackages(buildroot, revisionfile, board):
   _UprevAllPackages(buildroot)
 
 
-def _UprevCleanup(buildroot):
+def _UprevCleanup(buildroot, error_ok=False):
   """Clean up after a previous uprev attempt."""
   cwd = os.path.join(buildroot, 'src', 'scripts')
   RunCommand(['./cros_mark_as_stable', '--srcroot=..',
               '--tracking_branch="cros/master"', 'clean'],
-             cwd=cwd)
+             cwd=cwd, error_ok=error_ok)
 
 
 def _UprevPush(buildroot):

lib/cros_build_lib.py

@@ -34,6 +34,7 @@ def RunCommand(cmd, print_cmd=True, error_ok=False, error_message=None,
   stdout = None
   stderr = None
   stdin = None
+  output = ''
 
   # Modify defaults based on parameters.
   if redirect_stdout:  stdout = subprocess.PIPE
@@ -45,6 +46,7 @@ def RunCommand(cmd, print_cmd=True, error_ok=False, error_message=None,
   if print_cmd:
     Info('RunCommand: %s' % ' '.join(cmd))
 
+  try:
     proc = subprocess.Popen(cmd, cwd=cwd, stdin=stdin,
                             stdout=stdout, stderr=stderr)
     (output, error) = proc.communicate(input)
@@ -54,6 +56,11 @@ def RunCommand(cmd, print_cmd=True, error_ok=False, error_message=None,
     if not error_ok and proc.returncode:
       raise Exception('Command "%s" failed.\n' % (' '.join(cmd)) +
                       (error_message or error or output or ''))
+  except Exception,e:
+    if not error_ok:
+      raise
+    else:
+      Warning(str(e))
 
   return output