Build errors are not correct for unauthorized pushes

[jansepar]

From old repo.

@tedtate :

When I attempted to push to a project which the currently logged in user does not have access to I receive the following:

Build Complete.
[Error: Project not found. Check your project name in project.json.]

Please update the error so that the user is informed they don't have access to the requested project, not that it doesn't exist.

@johnboxall :

That was a conscious decision the same way you get a 404 for https://github.com/mobify/mobify-js-tools if you aren't logged in.

But we could also probably say 'check your credentials' : )

[johnboxall]

Currently the API returns a HTTP 404 if:

• The project name in project.json refers to a project that doesn't exist.
• The user doesn't have permissions to access the project.

We should improve the error message to suggest users:

1. Double check their project name in their project.json file.
2. Double check their saved credentials.