tools: enforce deepStrictEqual over deepEqual

Introduce a lint rule that enforces use of `assert.deepStrictEqual()`
over `assert.deepEqual()`.

.eslintrc

@@ -85,9 +85,10 @@ rules:
   prefer-const: 2
 
   # Custom rules in tools/eslint-rules
+  align-multiline-assignment: 2
   assert-fail-single-argument: 2
   new-with-error: [2, "Error", "RangeError", "TypeError", "SyntaxError", "ReferenceError"]
-  align-multiline-assignment: 2
+  no-deepEqual: 2
 
 # Global scoped method and vars
 globals:

tools/eslint-rules/no-deepEqual.js

@@ -0,0 +1,32 @@
+/**
+ * @fileoverview Prohibit use of assert.deepEqual()
+ * @author Rich Trott
+ *
+ * This rule is imperfect, but will find the most common forms of
+ * assert.deepEqual() usage.
+ */
+'use strict';
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+const msg = 'assert.deepEqual() disallowed. Use assert.deepStrictEqual()';
+
+function isAssert(node) {
+  return node.callee.object && node.callee.object.name === 'assert';
+}
+
+function isDeepEqual(node) {
+  return node.callee.property && node.callee.property.name === 'deepEqual';
+}
+
+module.exports = function(context) {
+  return {
+    'CallExpression': function(node) {
+      if (isAssert(node) && isDeepEqual(node)) {
+        context.report(node, msg);
+      }
+    }
+  };
+};