function expectObjectEqualsFailure(matcher, matchObject, opt_errorMsg) {
  mockExpect.errorMessages = [];
  assertFalse(matcher.matches(matchObject, mockExpect));
  assertNotEquals(0, mockExpect.getErrorMessageCount());
  if (opt_errorMsg) {
    assertContains(opt_errorMsg, mockExpect.errorMessages[0]);
  }
}
Utility method for checking for an ObjectEquals match failure.  Checks that
the expected error message was included in the error messages appended to
the expectation object.
@param {?} matcher
    The matcher to test against.
@param {!Object} matchObject The object to compare.
@param {string=} opt_errorMsg The deep object comparison failure message
    to check for.