Make the partition= tag optional.

Since we might use ToT release tools to sign a package
generated by an older build, we make the new
`partition=` tag optional. This also means we need to be
careful to use non-greedy regex matching.

Bug: 153133823
Test: python3 -m unittest
Test: input with and without the new `partition=` tag
Test: new test_ReadApkCerts_WithWithoutOptionalFields
Change-Id: Ic57efd34e745ad302ae17150c6f2318f0b4524cb

tools/releasetools/sign_target_files_apks.py

@@ -1082,8 +1082,8 @@ def ReadApexKeysInfo(tf_zip):
         r'public_key="(?P<PAYLOAD_PUBLIC_KEY>.*)"\s+'
         r'private_key="(?P<PAYLOAD_PRIVATE_KEY>.*)"\s+'
         r'container_certificate="(?P<CONTAINER_CERT>.*)"\s+'
-        r'container_private_key="(?P<CONTAINER_PRIVATE_KEY>.*)"\s+'
-        r'partition="(?P<PARTITION>.*)"$',
+        r'container_private_key="(?P<CONTAINER_PRIVATE_KEY>.*?)"'
+        r'(\s+partition="(?P<PARTITION>.*?)")?$',
         line)
     if not matches:
       continue