OpenSSL::SSL::SSLError: SSL_connect SYSCALL returned=5 errno=0 state=SSLv3 read server hello A

openssl version
 OpenSSL 0.9.8zh 14 Jan 2016

which openssl
  /usr/bin/openssl

ruby -v
  ruby 2.1.6p336 (2015-04-13 revision 50298) [x86_64-darwin14.0]

rbenv -v
  rbenv 0.4.0

cert    = File.read(File.join(Rails.root, 'ssl', 'test_env', 'their_test_cert.der'))
ca_file = File.read(File.join(Rails.root, 'ssl', 'test_env', 'Class3PublicPrimaryCA.der'))

uri     = URI("https://xml.theirtestenv.com/api/receive")

headers              = {
  'x-IK-Version'       => 'IKR/V4.00',
}

proxy_host = "myproxyhose"
proxy_port = "1234"
proxy_user = "myproxyuser"
proxy_pass = "myproxypass"

proxy_request = Net::HTTP.new(uri.hostname, '443', proxy_host, proxy_port, proxy_user, proxy_pass)

# http.key = OpenSSL::PKey::RSA.new(rsa_key)

proxy_request.use_ssl = true
proxy_request.cert = OpenSSL::X509::Certificate.new(cert)
proxy_request.ca_file = ca_file
proxy_request.verify_mode     = OpenSSL::SSL::VERIFY_PEER
# proxy_request.ssl_version     = :SSLv3
# This doesn't seem to matter whether I put this or not...

# Tried variations of these...
# proxy_request.ssl_version = :TLSv1
# proxy_request.ciphers = ['DES-CBC3-SHA']

post_request = Net::HTTP::Post.new(uri, headers)
post_request.content_type = "multipart/related"

response = proxy_request.request(post_request)
puts response.inspect