$ ./bin/test
Traceback (most recent call last):
  File "venv/bin/mypy", line 7, in <module>
    from mypy.__main__ import console_entry
  File "venv/lib/python3.6/site-packages/mypy/__main__.py", line 3, in <module>
    from mypy.main import main
  File "venv/lib/python3.6/site-packages/mypy/main.py", line 13, in <module>
    from mypy import build
  File "venv/lib/python3.6/site-packages/mypy/build.py", line 31, in <module>
    from mypy.nodes import (MypyFile, Node, ImportBase, Import, ImportFrom, ImportAll)
  File "venv/lib/python3.6/site-packages/mypy/nodes.py", line 11, in <module>
    import mypy.strconv
  File "venv/lib/python3.6/site-packages/mypy/strconv.py", line 10, in <module>
    from mypy.visitor import NodeVisitor
  File "venv/lib/python3.6/site-packages/mypy/visitor.py", line 304, in <module>
    class NodeVisitor(Generic[T], ExpressionVisitor[T], StatementVisitor[T]):
  File "/usr/lib/python3.6/typing.py", line 944, in __new__
    self = super().__new__(cls, name, bases, namespace, _root=True)
  File "/usr/lib/python3.6/typing.py", line 118, in __new__
    return super().__new__(cls, name, bases, namespace)
  File "venv/lib/python3.6/abc.py", line 133, in __new__
    cls = super().__new__(mcls, name, bases, namespace)
TypeError: Cannot create a consistent method resolution
order (MRO) for bases Generic, ExpressionVisitor, StatementVisitor