Remove usage of CHECK_NOTNULL

We want to switch to absl logging instead of glog.  gtest and ceres are
going there, and we already have absl as a dependency.  ABSL doesn't
have CHECK_NOTNULL, and we can move things over in an easier to review
fashion.

Change-Id: Ifd9a11ec34a2357cec43f88dba015db9c28ed2cf
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/y2020/control_loops/drivetrain/localizer_test.cc b/y2020/control_loops/drivetrain/localizer_test.cc
index ca25137..e509241 100644
--- a/y2020/control_loops/drivetrain/localizer_test.cc
+++ b/y2020/control_loops/drivetrain/localizer_test.cc
@@ -215,7 +215,8 @@
     // Run for enough time to allow the gyro/imu zeroing code to run.
     RunFor(std::chrono::seconds(15));
     CHECK(drivetrain_status_fetcher_.Fetch());
-    EXPECT_TRUE(CHECK_NOTNULL(drivetrain_status_fetcher_->zeroing())->zeroed());
+    CHECK(drivetrain_status_fetcher_->zeroing() != nullptr);
+    EXPECT_TRUE(drivetrain_status_fetcher_->zeroing()->zeroed());
   }
 
   virtual ~LocalizedDrivetrainTest() override {}