rest-client is pinned to '~> 1.6.0' at the moment, blocking an update to a newer rbovirt. Also 1.6.9 has two security issues which are probably not critical for Foreman core, but won't get resolved in 1.6.x:

Name: rest-client
Version: 1.6.9
Advisory: CVE-2015-1820
Criticality: Unknown
URL: https://github.com/rest-client/rest-client/issues/369
Title: rubygem-rest-client: session fixation vulnerability via Set-Cookie headers in 30x redirection responses
Solution: upgrade to >= 1.8.0

Name: rest-client
Version: 1.6.9
Advisory: CVE-2015-3448
Criticality: Unknown
URL: http://www.osvdb.org/show/osvdb/117461
Title: Rest-Client Gem for Ruby logs password information in plaintext
Solution: upgrade to >= 1.7.3