Actually format the error message

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>
Don't use semicolons in error messages

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>
Correct verb

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>