Prebuilts should not gate normal builds if the server responds with an error.

parallel_emerge

 #!/usr/bin/python2.6
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Program to run emerge in parallel, for significant speedup.
 
 Usage:
  ./parallel_emerge [--board=BOARD] [--workon=PKGS] [--no-workon-deps]
                    [--force-remote-binary=PKGS] [emerge args] package
@@ skipping 730 matching lines @@
         url: The specified url.
         tries: The number of times to try.
 
       Returns:
         The result of urllib2.urlopen(url).
       """
       for i in range(tries):
         try:
           return urllib2.urlopen(url)
         except urllib2.HTTPError as e:
+          print "Cannot GET %s: %s" % (url, str(e))
           if i + 1 >= tries or e.code < 500:
             raise
-          else:
-            print "Cannot GET %s: %s" % (url, str(e))
         except urllib2.URLError as e:
+          print "Cannot GET %s: %s" % (url, str(e))
           if i + 1 >= tries:
             raise
-          else:
-            print "Cannot GET %s: %s" % (url, str(e))
         print "Sleeping for 10 seconds before retrying..."
         time.sleep(10)
 
     url = os.path.join(binhost_url, "Packages")
     try:
       f = retry_urlopen(url)
     except urllib2.HTTPError as e:
       if e.code == 404:
         return {}
       else:
@@ skipping 1058 matching lines @@
     print "Starting fast-emerge."
     print " Building package %s on %s" % (cmdline_packages,
                                           deps.board or "root")
     if nomerge_packages:
       print " Skipping package %s on %s" % (nomerge_packages,
                                             deps.board or "root")
 
   remote_pkgs = {}
   if "--getbinpkg" in emerge.opts:
     binhost = emerge.settings["PORTAGE_BINHOST"]
-    remote_pkgs = deps.RemotePackageDatabase(binhost)
+    try:
+      remote_pkgs = deps.RemotePackageDatabase(binhost)
+    except (urllib2.HTTPError, urllib2.URLError):
+      print "Cannot resolve binhost. Building from source..."
+      del emerge.opts["--getbinpkg"]
 
   deps_tree, deps_info = deps.GenDependencyTree(remote_pkgs)
 
   # You want me to be verbose? I'll give you two trees! Twice as much value.
   if "--tree" in emerge.opts and "--verbose" in emerge.opts:
     deps.PrintTree(deps_tree)
 
   deps_graph = deps.GenDependencyGraph(deps_tree, deps_info, remote_pkgs)
 
   # OK, time to print out our progress so far.
@@ skipping 43 matching lines @@
   # need to upgrade the rest of the packages. So we'll go ahead and do that.
   if portage_upgrade:
     args = sys.argv[1:] + ["--nomerge=sys-apps/portage"]
     os.execvp(os.path.realpath(sys.argv[0]), args)
 
   print "Done"
   sys.exit(0)
 
 if __name__ == "__main__":
   main()