Solved this part using another docker image. Now we have a rate limit error:
Creating/renewal test.roipost.com certificates... (test.roipost.com)
2017-07-10 10:42:20,863:INFO:simp_le:1211: Generating new account key
2017-07-10 10:42:27,102:INFO:requests.packages.urllib3.connectionpool:756: Starting new HTTPS connection (1): acme-v01.api.letsencrypt.org
ACME server returned an error: urn:acme:error:rateLimited :: There were too many requests of a given type :: Error creating new registration :: too many registrations for this IP
Debugging tips: -v improves output verbosity. Help is available under --help.