isAnimatedGif fails on local domain

[rikwillems]

My development setup is based on Valet Plus. Local usage of this module results in this error:

[2020-01-20 09:18:12] main.ERROR: Staempfli_ImageResizer: could not find image: 
Warning: fopen(): SSL operation failed with code 1. OpenSSL Error messages:
error:14090086:SSL routines:ssl3_get_server_certificate:certificate verify failed in vendor/staempfli/magento2-module-image-resizer/Model/Resizer.php on line 318 [] []