Put error messages on one line
Put error messages on one line

Error messages are helpful. They are doubly helpful when a user can grep
the source tree for the error string and find where they are. Splitting
the message over multiple lines breaks this.

If someone has a PEP8 compliant variant of this commit I'd be happy to
follow their example, as long as the strings are unbroken.

Signed-off-by: Joel Stanley <4816dabf8db1bc6cac35b3a24cab2ff844b5b0c7@jms.id.au>

open-power/op-test-framework,open-power/op-test-framework,open-power/op-test-framework