Missing header file prevents pip installation

Created by: chadhanna

When doing pip install I see:

In file included from src/kerberos.c:19:0:
src/kerberosbasic.h:17:10: fatal error: gssapi/gssapi.h: No such file or directory
 #include <gssapi/gssapi.h>

which was fixed by doing:

sudo apt-get install libkrb5-dev

Could this be added as a dependency?