paygen_build_lib: Fix unit tests to reflect change in Autotest.

CQ-DEPEND=CL:303746
BUG=b:24405484
TEST=Unit tests

Change-Id: Ife0cbb3535ed6bce43b1f56d2706ca7ca008237f
Reviewed-on: https://chromium-review.googlesource.com/303960
Commit-Ready: Gilad Arnold <garnold@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Matthew Sartori <msartori@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
diff --git a/lib/paygen/paygen_build_lib_unittest.py b/lib/paygen/paygen_build_lib_unittest.py
index 41169a5..85c8e16 100644
--- a/lib/paygen/paygen_build_lib_unittest.py
+++ b/lib/paygen/paygen_build_lib_unittest.py
@@ -1533,7 +1533,7 @@
 target_release = '1.2.3'
 target_payload_uri = 'None'
 SUITE = 'paygen_foo'
-source_image_uri = 'gs://foo/bar.tar.bz2'
+source_payload_uri = 'gs://foo/bar.tar.bz2'
 source_archive_uri = 'gs://chromeos-releases/foo-channel/foo-board/1.2.3'
 
 AUTHOR = "Chromium OS"