Mercurial https clone: "abort: error: (...) wrong version number"

You probably have to disable TLS, read this

To do so, add this to ~/.hgrc

[ui]
tls = False

more information about SSL and TLS here

There is another cause. It might not have been your problem, but it should be listed here as well, for the case others encounter this problem:

If you are behind a proxy and your proxy settings are incorrect, this error message appears as well. God knows why...

Example: you have the following config

[http_proxy]
no = localhost,127.0.0.1
host = 1.2.3.4:8080
user = myusername
passwd = oldpassword

The oldpassword might be obsolet (you have forgotten to change it). Then the very same SSL wrong version error appears. It does absolutly make no sense at all (at least to me), but I reproduced this issue with mercurial 3.6.2. Correcting the proxy settings fixes everything.

Not exactly a direct solution but good workaround: With strong suggestion that the problem lies is ssl I have switched to ssh(https://confluence.atlassian.com/pages/viewpage.action?pageId=270827678) and now everything works. So from a practical point of view for me this problem is solved.