cli/scripts: more cros_build_lib.run API migrations

BUG=b:187789262
TEST=CQ passes

Change-Id: Idcc78ccfe14fdbae89ae7573d6e78036bdacf8ad
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3738519
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Ram Chandrasekar <rchandrasekar@google.com>
Auto-Submit: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Ram Chandrasekar <rchandrasekar@google.com>
diff --git a/cli/flash_unittest.py b/cli/flash_unittest.py
index 3aef0f3..08a9944 100644
--- a/cli/flash_unittest.py
+++ b/cli/flash_unittest.py
@@ -165,7 +165,7 @@
     op = flash.UsbImagerOperation('foo')
     self.PatchObject(osutils, 'IsChildProcess', return_value=True)
     self.rc.AddCmdResult(partial_mock.Ignore(),
-                         output='%d\n10\n' % expected_pid)
+                         stdout=f'{expected_pid}\n10\n')
 
     pid = op._GetDDPid()
 
@@ -177,7 +177,7 @@
     expected_pid = -1
     op = flash.UsbImagerOperation('foo')
     self.PatchObject(osutils, 'IsChildProcess', return_value=False)
-    self.rc.AddCmdResult(partial_mock.Ignore(), output='5\n10\n')
+    self.rc.AddCmdResult(partial_mock.Ignore(), stdout='5\n10\n')
 
     pid = op._GetDDPid()