message: Upgrade pip for python2.7 in custom op docker files.
diff: set -e
  -# We don't apt-get install so that we can install a newer version of pip.
  -# Only needed for Ubuntu 14.04 and 16.04; not needed for 18.04 and Debian 8,9?
  -# Run easy_install after easy_install3, so that the default pip points to pip2,
  -# to match the default python version of 2.7.
  -easy_install3 -U pip==18.1
  -easy_install -U pip==18.1
  +# Get the latest version of pip so it recognize manylinux2010
  +pip2 install --upgrade pip
  +pip3 install --upgrade pip
  # Install pip packages from whl files to avoid the time-consuming process of
  # building from source.
  