Despite trying very hard to keep dicts out of our hash algorithm, we seem
to still accidentally add them in ways that the tests can't catch. This
can cause errors when hashes are not computed deterministically.
This fixes an error we saw with Python 3.5, where dictionary iteration
order is random. In this instance, we saw a bug when reading Spack
environment lockfiles -- The load would fail like this:
```
...
File "/sw/spack/lib/spack/spack/environment.py", line 1249, in concretized_specs
yield (s, self.specs_by_hash[h])
KeyError: 'qcttqplkwgxzjlycbs4rfxxladnt423p'
```
This was because the hashes differed depending on whether we wrote `path`
or `module` first when recomputing the build hash as part of reading a
Spack lockfile. We can fix it by ensuring a determistic iteration order.
- [x] Fix two places (one that caused an issue, and one that did
not... yet) where our to_node_dict-like methods were using regular python
dicts.
- [x] Also add a check that statically analyzes our to_node_dict
functions and flags any that use Python dicts.
The test found the two errors fixed here, specifically:
```
E AssertionError: assert [] == ['Use syaml_dict instead of ...pack/spack/spec.py:1495:28']
E Right contains more items, first extra item: 'Use syaml_dict instead of dict at /Users/gamblin2/src/spack/lib/spack/spack/spec.py:1495:28'
E Full diff:
E - []
E + ['Use syaml_dict instead of dict at '
E + '/Users/gamblin2/src/spack/lib/spack/spack/spec.py:1495:28']
```
and
```
E AssertionError: assert [] == ['Use syaml_dict instead of ...ack/architecture.py:359:15']
E Right contains more items, first extra item: 'Use syaml_dict instead of dict at /Users/gamblin2/src/spack/lib/spack/spack/architecture.py:359:15'
E Full diff:
E - []
E + ['Use syaml_dict instead of dict at '
E + '/Users/gamblin2/src/spack/lib/spack/spack/architecture.py:359:15']
```
2eadfa24e9