Incorrect error when malformed project.conf is found

Summary

If a malformed project.conf is present, bst reports that it could not be found, rather than reporting the error found in the file.

Steps to reproduce

Using the latest bst-1.2 branch, cause an error in the project.conf such as "%{variable, such as a missing closing quotation.

Run bst inside the project directory that contains the malformed file.

What is the current bug behavior?

You will see that it can not find the project.conf, even though it is present.

However if you pass "n" to the prompt, which asks if you would like bst to create one, you will then see the correct error that is causing the project.conf to be malformed.

What is the expected correct behavior?

Display the known error with project.conf, instead of reporting that it could not be found.

Relevant logs and/or screenshots

Possible fixes

Other relevant information

• BuildStream version affected: /milestone %BuildStream_v1.2

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