test: validate full error messages

test: changed test2 of test-vm-timeout.js so that entire error message
      would be matched in assert.throw.

      Before test 2 of test-vm-timeout.js would match any RangeError,
      now it looks specifically for the error message
      "RangeError: timeout must be a positive number"

test: changed test 3 of test-vm-timeout.js so that entire error message
      would be matched in assert.throw.

      Before test 3 of test-vm-timeout.js would match any RangeError,
      now it looks specifically for the error message
      "RangeError: timeout must be a positive number"

PR-URL: https://github.com/nodejs/node/pull/13453
Refs: https://github.com/nodejs/node/issues/13454
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>

test/parallel/test-vm-timeout.js

@@ -32,12 +32,12 @@ assert.throws(function() {
 // Test 2: Timeout must be >= 0ms
 assert.throws(function() {
   vm.runInThisContext('', { timeout: -1 });
-}, RangeError);
+}, /^RangeError: timeout must be a positive number$/);
 
 // Test 3: Timeout of 0ms
 assert.throws(function() {
   vm.runInThisContext('', { timeout: 0 });
-}, RangeError);
+}, /^RangeError: timeout must be a positive number$/);
 
 // Test 4: Timeout of 1000ms, script finishes first
 vm.runInThisContext('', { timeout: 1000 });