releasetools: Fix an issue with pubkey extraction.

When calling 'openssl x509 -pubkey' to extract the public key from a
certificate, openssl 1.0 and 1.1 handle the '-out' parameter
differently. openssl 1.0 doesn't write the output into the specified
filename, which leads to the payload verification failure in
check_ota_package_signature.VerifyAbOtaPayload(). This CL addresses
the issue by always collecting the output from stdout instead.

It also refactors the two copies into common.ExtractPublicKey(), and
adds unittest. get_testdata_dir() is moved into test_utils.py that holds
common utils for running the unittests.

Bug: 72884343
Test: python -m unittest test_common
Test: python -m unittest test_ota_from_target_files
Test: Run sign_target_files_apks with '--replace_ota_keys' on marlin
      target_files zip. Check the payload pubkey replacement.
Test: Trigger the tests with forrest, and tests no longer fail on
      machines with openssl 1.0.1.
Change-Id: Ib0389b360f064053e9aa7cc0546d718e7b23003b

tools/releasetools/test_utils.py

@@ -0,0 +1,28 @@
+#
+# Copyright (C) 2018 The Android Open Source Project
+#
+# 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.
+#
+
+"""
+Utils for running unittests.
+"""
+
+import os.path
+
+
+def get_testdata_dir():
+  """Returns the testdata dir, in relative to the script dir."""
+  # The script dir is the one we want, which could be different from pwd.
+  current_dir = os.path.dirname(os.path.realpath(__file__))
+  return os.path.join(current_dir, 'testdata')