Improve keyboard interrupt handling
Improve keyboard interrupt handling

Summary: Print "^C\n" instead of KeyboardInterrupt

Test Plan: existing tests

Reviewers: psung

Reviewed By: psung

Differential Revision: https://phabricator.dnanexus.com/D168

jhuttner/dx-toolkit,olegnev/dx-toolkit,jhuttner/dx-toolkit,dnanexus/dx-toolkit,olegnev/dx-toolkit,andyshinn/dx-toolkit,dnanexus/dx-toolkit,dnanexus/dx-toolkit,olegnev/dx-toolkit,dnanexus/dx-toolkit,dnanexus/dx-toolkit,olegnev/dx-toolkit,andyshinn/dx-toolkit,johnwallace123/dx-toolkit,jhuttner/dx-toolkit,andyshinn/dx-toolkit,andyshinn/dx-toolkit,johnwallace123/dx-toolkit,johnwallace123/dx-toolkit,johnwallace123/dx-toolkit,andyshinn/dx-toolkit,jhuttner/dx-toolkit,andyshinn/dx-toolkit,johnwallace123/dx-toolkit,andyshinn/dx-toolkit,olegnev/dx-toolkit,dnanexus/dx-toolkit,andyshinn/dx-toolkit,jhuttner/dx-toolkit,johnwallace123/dx-toolkit,johnwallace123/dx-toolkit,olegnev/dx-toolkit,dnanexus/dx-toolkit,jhuttner/dx-toolkit,johnwallace123/dx-toolkit,olegnev/dx-toolkit,jhuttner/dx-toolkit,olegnev/dx-toolkit,dnanexus/dx-toolkit,jhuttner/dx-toolkit