Instead of sitting mysteriously alone in internals/utils.py

This is not an error related to loading data, like a parse error
in the quota specification is, but a problem raised by the artifact
cache - this allows us to assert more specific machine readable
errors in test cases (instead of checking the string in stderr, which
this patch also fixes).

This also removes a typo from the error message in the said error.

  * tests/artifactcache/cache_size.py

    Updated test case to expect the artifact error, which consequently
    changes the test case to properly assert a machine readable error
    instead of asserting text in the stderr (which is the real, secret
    motivation behind this patch).

  * tests/artifactcache/expiry.py: Reworked test_invalid_cache_quota()

    Now expect the artifact error for the tests which check configurations
    which create caches too large to fit on the disk.

Tristan/insufficient storage error

See merge request !1102

Instead of a single target, we can always provide a single target
in a list.

Reduce number of calls to `bst show` in tests

See merge request !1103

Tristan Van Berkom authored Jan 24, 2019 and Tristan Van Berkom committed Jan 24, 2019

This tests how BuildStream reacts when it fails to write the tracking
results to the element files or project.refs file, which is an operation
that plugins do not play a part in.

As such, removing the per repo kind parameterization from this test
as multiple runs are redundant here.

test_track_error_cannot_write_file() fixup

See merge request !1104

Jonathan Maw authored Jan 04, 2019 and Jürg Billeter committed Jan 24, 2019

Previously, it merely tested that buildstream did not fall other,
rather than whether it did anything useful.

Jonathan Maw authored Jan 07, 2019 and Jürg Billeter committed Jan 24, 2019

Previously, there was no way of detecting whether fetching happened, as
an element with an open workspace will not be fetched.

Add tests to cover reinstated support for guessing targets

See merge request !1042