check for invalid bootstrap

Author: zworkb

pythonforandroid/toolchain.py

@@ -984,8 +984,9 @@ def _build_package(self, args, package_type):
         ctx = self.ctx
         dist = self._dist
         bs = Bootstrap.get_bootstrap(args.bootstrap, ctx)
+        if not bs:
+            raise BuildInterruptingException("invalid bootstrap given: %s" % args.bootstrap)
         ctx.prepare_bootstrap(bs)
-
         self._fix_args(args)
         env = self._prepare_release_env(args)