message: Fixed typo
  Closes
diff: @@ -543,7 +543,7 @@ output-expectations test:
  expected to hit the backstop timeout.)
  * `expect-stdout:` All subsequent tokens on the line are concatenated,
  - with spaces in between, and a newline is appeneded. The PhantomJS
  + with spaces in between, and a newline is appended. The PhantomJS
  process is expected to emit that text, verbatim, on its standard
  output. If used more than once, that produces multiple lines of
  expected output.
  