class ChefConfig::Config

def self.proxy_uri(scheme, host, port)

is returned
set environment variables, unless exluded by no_proxy, in which case nil
Given a scheme, host, and port, return the correct proxy URI based on the 
def self.proxy_uri(scheme, host, port)
  proxy_env_var = ENV["#{scheme}_proxy"].to_s.strip
  # Check if the proxy string contains a scheme. If not, add the url's scheme to the
  # proxy before parsing. The regex /^.*:\/\// matches, for example, http://. Reusing proxy
  # here since we are really just trying to get the string built correctly.
  proxy = if !proxy_env_var.empty?
            if proxy_env_var =~ /^.*:\/\//
              URI.parse(proxy_env_var)
            else
              URI.parse("#{scheme}://#{proxy_env_var}")
            end
          end
  return proxy unless fuzzy_hostname_match_any?(host, ENV["no_proxy"])
end