verify_ocsp_response() assumes OCSP response has reason

When performing OCSP revocation checks against https://revoked.badssl.com/ using the function certvalidator.validate.verify_ocsp_response() I get the following:

Traceback (most recent call last):
...
  File "/.../venv/lib/python3.6/site-packages/certvalidator/validate.py", line 1101, in verify_ocsp_response
    reason = revocation_info['revocation_reason'].human_friendly
AttributeError: 'Void' object has no attribute 'human_friendly'

It seems that the function assumes that a revocation reason is given, whereas the RFC states (end of https://tools.ietf.org/html/rfc6960#section-4.2.1) that revocation reason is optional (revocationReason [0] EXPLICIT CRLReason OPTIONAL), and hence revocation_info['revocation_reason'] can be an instance of Void. I would therefore suggest that verify_ocsp_response() should check whether revocation_info['revocation_reason'] is Void first before trying get the human_friendly property, or that Void should have a human_friendly property.

Start in certvalidator/validate.py at verify_ocsp_response(), especially the revocation_reason handling around line 1101. Reproduce the failure against https://revoked.badssl.com/ and inspect how an absent reason is represented. Done means the optional OCSP revocation reason no longer causes an AttributeError.