Log warnings instead of errors for missing TLS certs

[github-actions]

This is an automatic cherry-pick of 9d13ad42aef15df2c55c9f78b8813b6bee8cee68

The original PR was #192 with message:

Checklist before requesting a review

• I have performed a self-review of my own code
• I have verified that the code builds perfectly fine on my local system
• I have added tests that prove my fix is effective or that my feature works
• I have commented my code, particularly in hard-to-understand areas
• I have verified that my code follows the style already available in the repository
• I have made corresponding changes to the documentation