Add a new return code for internal linear solve failures

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 31.72%. Comparing base (1238b2b) to head (0a3b794).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #677 +/- ## ======================================= Coverage 31.72% 31.72% ======================================= Files 55 55 Lines 4505 4505 ======================================= Hits 1429 1429 Misses 3076 3076 ```

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