setup_board: add user friendly error message for bad --board values

BUG=chromium:618729
TEST=`setup_board --board=foobar` prints a helpful message

Change-Id: Ic8a16e15f99b8e19f7396fad71bc3b13f624a0e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1772038
Reviewed-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/setup_board.py b/scripts/setup_board.py
index d1126b9..79f0429 100644
--- a/scripts/setup_board.py
+++ b/scripts/setup_board.py
@@ -16,6 +16,7 @@
 from chromite.lib import build_target_util
 from chromite.lib import commandline
 from chromite.lib import cros_build_lib
+from chromite.lib import portage_util
 from chromite.service import sysroot
 
 
@@ -131,5 +132,11 @@
   opts = _ParseArgs(argv)
   try:
     sysroot.SetupBoard(opts.build_target, opts.accept_licenses, opts.run_config)
+  except portage_util.MissingOverlayError as e:
+    # Add a bit more user friendly message as people can typo names easily.
+    cros_build_lib.Die(
+        '%s\n'
+        "Double check the --board setting and make sure you're syncing the "
+        'right manifest (internal-vs-external).', e)
   except sysroot.Error as e:
     cros_build_lib.Die(e.message)