gistfile1.rb

# Works just fine
uri = URI('https://api.twitter.com/1.1/statuses/mentions_timeline.json')

http = Net::HTTP.new(uri.hostname, uri.port)
http.use_ssl = true

req = Net::HTTP::Get.new(uri)

res = http.request(req)
puts res.body

# Results in an error

uri = URI('https://rink.hockeyapp.net/api/2/auth_tokens')

http = Net::HTTP.new(uri.hostname, uri.port)
http.use_ssl = true

req = Net::HTTP::Get.new(uri)

res = http.request(req)

# The aforementioned error
SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed

Checking OpenSSL version used by Ruby:

bundle exec irb 

'2.0.0-p576 :001 > OpenSSL::OPENSSL_LIBRARY_VERSION
 => "OpenSSL 1.0.2a 19 Mar 2015" 

It appears that using anything that is later than 1.0.1j (version from Sept 2014 AFAIR) causes this issue.