feat: Add the assert.fail([message]) interface

In relation to chaijs#1116, the `assert.fail` interface should accept
ibeing called with only 1 arguments to fail with a custom message.

lib/chai/interface/assert.js

@@ -41,6 +41,7 @@ module.exports = function (chai, util) {
   };
 
   /**
+   * ### .fail([message])
    * ### .fail(actual, expected, [message], [operator])
    *
    * Throw a failure. Node.js `assert` module-compatible.
@@ -55,6 +56,13 @@ module.exports = function (chai, util) {
    */
 
   assert.fail = function (actual, expected, message, operator) {
+    if (arguments.length < 2) {
+        // Comply with Node's fail([message]) interface
+
+        message = actual;
+        actual = expected = undefined;
+    }
+
     message = message || 'assert.fail()';
     throw new chai.AssertionError(message, {
         actual: actual

test/assert.js

@@ -20,6 +20,12 @@ describe('assert', function () {
     }).to.throw(chai.AssertionError, /this has failed/);
   });
 
+  it('fail', function () {
+    chai.expect(function () {
+      assert.fail('this has failed');
+    }).to.throw(chai.AssertionError, /this has failed/);
+  });
+
   it('isTrue', function () {
     assert.isTrue(true);