test-ui-color.py failure in Emacs shell-mode

[Jesse Glick]

M-x shell and run tests (as of 979b1b7340fb) fails with:

--- tests/test-ui-color.py.out
+++ tests/test-ui-color.py.err
@@ -1,5 +1,5 @@
  warning
  error
  'buffered\n'
-colored? True
-colored? True
+colored? False
+colored? False