Not able to update PATH variable: need to uninstall system bundle gem

Build Environment
1

Trying to run command: sudo gem install --user-install bundler -v 1.14.6
but I am getting error as below.
WARNING: You don’t have /root/.gem/ruby/2.1.0/bin in your PATH,
gem executables will not run.

my circleci commands:

- run: 
    name: Make Composer executables available globally 
    command: | 
      echo 'export PATH=$HOME/.gem/ruby/2.1.0/bin:$PATH' >> $BASH_ENV 
      source /home/circleci/.bashrc
2

Which image are you using and which user is the build running as?