Just use "pip" not "pip3"
Just use "pip" not "pip3"

Travis should be able to figure out which is meant, since we're running
on Python 3.7.

Signed-off-by: mulhern <7b51bcf507bcd7afb72bf8663752c0ddbeb517f6@redhat.com>

stratis-storage/stratisd,stratis-storage/stratisd,stratis-storage/stratisd