Please check your server extension called fileinfo, set false to APP_DEBUG in .env file
If still it’s show error, please wait until 08 September 2017, because of you may already seen our notice about vacation in right sidebar, we are including also here.
Due to a vacation, our office will be close from 29 August 2017 to 08 September 2017, in this time, we may unable to provide any support. But keep asking your question on our forums. We will start support again as soon as possible after open office.
Sorry for the inconvenience.