Lots of AST errors when trying to transpile Python to Rust
I was toying with the idea of parallelizing typchecking in mypy, and faced with the sad state of parallelism in Python I figured I would try to transpile mypy to rust for shits and giggles, to see how far py2many is from tackling a sizeable production codebase.

Turns out: pretty far, as evidenced by the (trimmed) output from running `py2many` on the `mypy` folder in the mypy git repo:

```
$ py2many --rust=1 --outdir=mypy_rs --project=mypy mypy/
Transpiling whole directory to mypy_rs:
binder.py:528:32: py2many.exceptions.AstUnrecognisedBinOp: List <class 'ast.Mult'> int
checker.py: AttributeError: 'Name' object has no attribute 'assigned_from'
checkexpr.py:2506:66: py2many.exceptions.AstUnrecognisedBinOp: List <class 'ast.Mult'> int
checkpattern.py:402:16: py2many.exceptions.AstUnrecognisedBinOp: int <class 'ast.Sub'> None
checkstrformat.py:748:31: py2many.exceptions.AstUnrecognisedBinOp: List <class 'ast.Mult'> int
config_parser.py: TypeError: sequence item 1: expected str instance, ellipsis found
constraints.py: TypeError: sequence item 1: expected str instance, ellipsis found
dmypy_server.py:129:29: py2many.exceptions.AstClassUsedBeforeDeclaration: Declaration of Server not yet parsed
errors.py:836:14: py2many.exceptions.AstClassUsedBeforeDeclaration: Declaration of CompileError not yet parsed
fastparse.py:502:30: py2many.exceptions.AstClassUsedBeforeDeclaration: Declaration of FindAttributeAssign not yet parsed
fixup.py:62:26: py2many.exceptions.AstClassUsedBeforeDeclaration: Declaration of TypeFixer not yet parsed
inspections.py: AttributeError: 'Module' object has no attribute 'scopes'
literals.py: TypeError: sequence item 1: expected str instance, ellipsis found
meet.py:664:25: py2many.exceptions.AstUnrecognisedBinOp: List <class 'ast.Mult'> int
messages.py:523:16: py2many.exceptions.AstNotImplementedError: sequence item 1: expected str instance, ellipsis found
modulefinder.py: TypeError: sequence item 1: expected str instance, ellipsis found
nodes.py:688:24: py2many.exceptions.AstUnrecognisedBinOp: Final <class 'ast.Add'> None
options.py:61:4: py2many.exceptions.AstUnrecognisedBinOp: Final <class 'ast.BitOr'> None
plugins/attrs.py: AttributeError: 'Module' object has no attribute 'scopes'
plugins/dataclasses.py:300:16: py2many.exceptions.AstUnrecognisedBinOp: str <class 'ast.Add'> Final
plugins/default.py: AttributeError: 'Module' object has no attribute 'scopes'
reachability.py: TypeError: sequence item 1: expected str instance, ellipsis found
semanal.py:5795:29: py2many.exceptions.AstUnrecognisedBinOp: List <class 'ast.Mult'> int
semanal_namedtuple.py:656:12: py2many.exceptions.AstUnrecognisedBinOp: str <class 'ast.Add'> Final
semanal_typeargs.py:137:25: py2many.exceptions.AstNotImplementedError: sequence item 1: expected str instance, ellipsis found
server/astmerge.py: TypeError: sequence item 1: expected str instance, ellipsis found
server/update.py:795:25: py2many.exceptions.AstNotImplementedError: unhashable type: 'list'
suggestions.py:738:26: py2many.exceptions.AstClassUsedBeforeDeclaration: Declaration of TypeFormatter not yet parsed
test/testcheck.py:121:19: py2many.exceptions.AstNotImplementedError: unhashable type: 'list'
test/teststubtest.py:234:4: py2many.exceptions.AstNotImplementedError: sequence item 0: expected str instance, ellipsis found
test/testtypes.py:684:12: py2many.exceptions.AstUnrecognisedBinOp: List <class 'ast.Mult'> int
test/typefixture.py:260:26: py2many.exceptions.AstUnrecognisedBinOp: List <class 'ast.Mult'> int
treetransform.py:187:15: py2many.exceptions.AstClassUsedBeforeDeclaration: Declaration of FuncMapInitializer not yet parsed
typeanal.py:1743:18: py2many.exceptions.AstClassUsedBeforeDeclaration: Declaration of FindTypeVarVisitor not yet parsed
typeops.py:804:29: py2many.exceptions.AstUnrecognisedBinOp: List <class 'ast.Mult'> int
types.py:2228:27: py2many.exceptions.AstUnrecognisedBinOp: List <class 'ast.Mult'> None
util.py:759:26: py2many.exceptions.AstUnrecognisedBinOp: int <class 'ast.Sub'> Final
build.py:508:29: py2many.exceptions.AstClassUsedBeforeDeclaration: Declaration of DefaultPlugin not yet parsed
```

I'm guessing a lot of it has to do with supporting recent type hint syntax?