Handles missing classes.jar in aar_import gracefully, by creating an empty jar file instead of crashing Bazel.

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MOS_MIGRATED_REVID=135405636
diff --git a/tools/zip/embedded_jar_extractor_test.py b/tools/zip/embedded_jar_extractor_test.py
new file mode 100644
index 0000000..568e0b3
--- /dev/null
+++ b/tools/zip/embedded_jar_extractor_test.py
@@ -0,0 +1,50 @@
+# Copyright 2016 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Tests for embedded_jar_extractor."""
+
+import filecmp
+import os
+import unittest
+import zipfile
+
+from tools.zip import embedded_jar_extractor
+
+
+class EmbeddedJarExtractorTest(unittest.TestCase):
+  """Unit tests for embedded_jar_extractor.py."""
+
+  def testPassingJarFile(self):
+    bjar = zipfile.ZipFile("b.jar", "w")
+    bjar.close()
+    azip = zipfile.ZipFile("a.zip", "w")
+    azip.write("b.jar")
+    azip.close()
+    if not os.path.exists("output"):
+      os.mkdir("output")
+    embedded_jar_extractor.ExtractEmbeddedJar("a.zip", "b.jar", "output")
+    self.assertTrue(filecmp.cmp("b.jar", "output/b.jar"))
+
+  def testMissingJarFile(self):
+    azip = zipfile.ZipFile("a.zip", "w")
+    azip.close()
+    if not os.path.exists("output"):
+      os.mkdir("output")
+    embedded_jar_extractor.ExtractEmbeddedJar("a.zip", "b.jar", "output")
+    bjar = zipfile.ZipFile("output/b.jar", "r")
+    self.assertEqual(["META-INF/MANIFEST.MF"], bjar.namelist())
+
+
+if __name__ == "__main__":
+  unittest.main()