SSL cert failures with Gmail accounts (mutt-wizard)

This actually isn't a mutt-wizard-specific problem, but I've been getting a lot of questions about it since mutt-wizard relies on offlineimap and ergo OpenSSL. Long story short, if you have updated Arch Linux recently, your new version of offlineimap/OpenSSL might give you a certificate error when attempting to sync with a Gmail account.

To solve this, do one of the following:

See the Github Issue that GrimKriegor opened on the mutt-wizard repo about this, with links to the relevant sources.