If there is an error comparing traitlet values when setting a trait, default to go ahead and notify of the new value.
fix pyreadline import in rlineimpl

it installs readline.py
Merge pull request #5210 from minrk/pyreadline

fix pyreadline import in rlineimpl
Merge pull request #5197 from jasongrout/traitlet-notify

If there is an error comparing traitlet values when setting a trait, default to go ahead and notify of the new value.