Fix mypy checking

Make mypy check our nested namespace packages by putting dbt in the mypy_path.
Fix a number of exposed mypy/type checker complaints. The checker mostly
passes now even if you add `--check-untyped-defs`, though there are a couple lingering issues so I'll leave that out of CI
Change the return type of RunOperation a bit - adds a couple fields to appease mypy

Also, bump the mypy version (it catches a few more issues).


automatic commit by git-black, original commits:
  32c5679
  9cc7a7a

core/dbt/task/list.py

@@ -43,9 +43,7 @@ def __init__(self, args, config):
         super().__init__(args, config)
         if self.args.models:
             if self.args.select:
-                raise RuntimeException(
-                    '"models" and "select" are mutually exclusive arguments'
-                )
+                raise RuntimeException('"models" and "select" are mutually exclusive arguments')
             if self.args.resource_types:
                 raise RuntimeException(
                     '"models" and "resource_type" are mutually exclusive ' "arguments"