error:
installing capybara-webkit 1.11.1 native extensions gem::ext::builderror: error: failed build gem native extension. current directory: /usr/local/rvm/gems/ruby-2.3.1/gems/capybara-webkit-1.11.1 /usr/local/rvm/rubies/ruby-2.3.1/bin/ruby -r ./siteconf20160607-31306-ngtugv.rb extconf.rb *** extconf.rb failed *** not create makefile due reason, lack of necessary libraries and/or headers. check mkmf.log file more details. may need configuration options. provided configuration options: --with-opt-dir --without-opt-dir --with-opt-include --without-opt-include=${opt-dir}/include --with-opt-lib --without-opt-lib=${opt-dir}/lib --with-make-prog --without-make-prog --srcdir=. --curdir --ruby=/usr/local/rvm/rubies/ruby-2.3.1/bin/$(ruby_base_name) --with-gl-dir --without-gl-dir --with-gl-include --without-gl-include=${gl-dir}/include --with-gl-lib --without-gl-lib=${gl-dir}/lib --with-zlib-dir --without-zlib-dir --with-zlib-include --without-zlib-include=${zlib-dir}/include --with-zlib-lib --without-zlib-lib=${zlib-dir}/lib command 'qmake ' not available extconf failed, exit code 1 gem files remain installed in /usr/local/rvm/gems/ruby-2.3.1/gems/capybara-webkit-1.11.1 inspection. results logged /usr/local/rvm/gems/ruby-2.3.1/extensions/x86_64-linux/2.3.0/capybara-webkit-1.11.1/gem_make.out
you seem lacking qt libraries on computer. there's nice tutorial on capybara-webkit github page showing how install it.
