fix BaseMailerTest class

[yus-ham]

Q	A
Is bugfix?	✔️
New feature?	❌
Breaks BC?	❌
Tests pass?	✔️
Fixed issues

[yii-bot]

Thank you for putting effort in the improvement of the Yii framework.
We have reviewed your pull request.

Unfortunately a use case is missing. It is required to get a better understanding of the pull request and helps us to determine the necessity and applicability of the suggested change to the framework.

Could you supply us with a use case please? Please be as detailed as possible and show some code!

Thanks!

This is an automated comment, triggered by adding the label pr:missing usecase.

[yus-ham]

My testing env resulting errors:

There were 6 errors:

1) yiiunit\framework\mail\BaseMailerTest::testSetupView
yii\base\Exception: Failed to create directory "/media/xubuncup/905C5F905C5F7048/cup/www/.dev/osp/yii2/tests/runtime/yiiunit\framework\mail\BaseMailerTest_27890": mkdir(): Invalid argument

[samdark]

What are your operating system and file system?

[yus-ham]

Here

xubuncup@ThinkPad-E440:/media/xubuncup/905C5F905C5F7048/cup/www/spionam-2.2$ php -v
PHP 7.3.12-1+ubuntu18.04.1+deb.sury.org+1 (cli) (built: Nov 28 2019 07:37:16) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.3.12, Copyright (c) 1998-2018 Zend Technologies
with Zend OPcache v7.3.12-1+ubuntu18.04.1+deb.sury.org+1, Copyright (c) 1999-2018, by Zend Technologies

[samdark]

OK. Looks valid.

[samdark]

Merged. Thanks!