sudo gem install bettercap

ERROR:  While executing gem ... (Gem::Exception)
    Unable to require openssl, install OpenSSL and rebuild ruby (preferred) or use non-HTTPS sources

gem source -r https://rubygems.org/
gem source -a http://rubygems.org/

ERROR:  While executing gem ... (Gem::Exception)
        Unable to require openssl, install OpenSSL and rebuild ruby (preferred) or use non-HTTPS sources

sudo gem install --local bettercap-1.6.2b.gem

ERROR:  Could not find a valid gem 'em-proxy' (>= 0.1.8, ~> 0.1) in any repository

2.4.5

ruby 2.2.2p95 (2015-04-13 revision 50295) [armv6l-linux-eabihf]