Pidgin needs to be built with gnutls to work with Hangouts

See https://github.com/EionRobb/purple-hangouts/issues/222

I can confirm that building Pidgin 2.14.1 from source with gnutls fixed this problem (and caused no new ones).

(purple-hangouts is not packaged in Debian/Ubuntu, but this is the case for Pidgin plugins for several widely-used protocols, such as Facebook Messenger and Skype IM. The plugins are easy to install from source or PPAs; it's a pity to make it harder for Ubuntu users by requiring them also to install Pidgin from source.)

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: pidgin 1:2.13.0-2.2ubuntu4
ProcVersionSignature: Ubuntu 5.4.0-51.56-generic 5.4.65
Uname: Linux 5.4.0-51-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.10
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: GNOME
Date: Fri Oct 23 00:31:46 2020
InstallationDate: Installed on 2019-12-23 (304 days ago)
InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
SourcePackage: pidgin
UpgradeStatus: Upgraded to focal on 2020-08-29 (54 days ago)