I'm creating this issue per @LukeTowers request in advance of the 460 release.
When navigating to Settings > Updates & Plugins > Install Plugins, a CURLOPT error is thrown.
I'm actually getting this error from the command line now as well:

However, I have been unable to reproduce again through the backend since I was originally notified by a colleague this morning of the error.
The official error is: 52 parameter must be a CURLOPT constant or equivalent integer
I traced it back some to the UpdateManager, and then to the Http facade L#182 in the Rain library.
When I was debugging this morning, I set $options = []; and it stopped throwing the error. For some reason though, when I removed this line and refreshed the page, the error went away.
@LarBearrr I know what it is - I will be rolling out a fix very shortly. :)
@bennothommo Thank you sir, just wanted to log it for the record. Want me to close or will you do that when you push the fix?
@LarBearrr I'll close this once the commit is made.
@LarBearrr This should now be fixed by https://github.com/octobercms/library/commit/ad7afd5e750d3aadcc1a4f2104378a8987654e77. Please let me know if there's any further issues.