Dump with filtered operators

[jmafoster1]

Summary

Dumping a database with filtered operators gives AttributeError: 'NoneType' object has no attribute 'value' because skipped jobs have no test outcome.

Steps to reproduce

1. Create file ROOT/mod.py with content

def func():
    return 1233 + 1

2. Create file ROOT/test_mod.py with content

import unittest
import mod

class Tests(unittest.TestCase):
    def test_func(self):
        self.assertEqual(mod.func(), 1234)

3. Create file ROOT/tutorial.toml with content

[cosmic-ray]
module-path = "mod.py"
timeout = 10.0
excluded-modules = []
test-command = "python -m unittest test_mod.py"

[cosmic-ray.distributor]
name = "local"

[cosmic-ray.filters.operators-filter]
exclude-operators = [
  "core/NumberReplacer"
]

4. Run cosmic-ray init tutorial.toml tutorial.sqlite
5. Run cr-filter-operators tutorial.sqlite tutorial.toml
6. Run cosmic-ray exec tutorial.toml tutorial.sqlite
7. Run cosmic-ray dump tutorial.sqlite
8. Observe error

cosmic_ray/cli.py", line 192, in result_to_dict
    d["test_outcome"] = d["test_outcome"].value
AttributeError: 'NoneType' object has no attribute 'value'

The problem comes about because the filtered jobs are skipped, so have no test_outcome. This could probably be fixed with a simple if statement in the line above to test whether d["test_outcome"] is not None before trying to access the value, although that might then pass the problem further down the line.

A fix is not a particularly high priority for me, but I thought I'd report the issue, and would be happy to attempt a pull request if that's something you're interested in.