Fix flake8_diff.sh when Travis runs in a fork
Fix flake8_diff.sh when Travis runs in a fork

The grep was not matching anything so the script exited with a 1 exit code.

karandesai-96/joblib,lesteve/joblib,karandesai-96/joblib,joblib/joblib,tomMoral/joblib,joblib/joblib,tomMoral/joblib,lesteve/joblib,aabadie/joblib,aabadie/joblib