Set price of agreement when sourcing with a framework
provide more meaningful test failure messages
rename test method
update the test

the PR is about setting the price from the FA on sourcing line, and the tests
were correct in the previous version when this was not the case.
Remove assert message to keep default explicit message
Merge pull request #39 from yvaucher/8.0-fa_sourcing-set-price

Set price of agreement when sourcing with a framework