squash! Bump mypy from 0.812 to 0.910 in /tools

This:

 * Deals with changes in how mypy handles metaclasses

 * Prefers sys.platform == "win32" due to
   python/mypy#8166 and mypy not having
   WindowsError defined by default any more

 * Installs various typestubs

 * Rewrites tox.ini to avoid duplicating everything, and allowing new
   versions of Python to be easily tested (as tox -e py310-mypy will
   now work without further changes).

tools/manifest/item.py

@@ -8,16 +8,7 @@
 MYPY = False
 if MYPY:
     # MYPY is set to True when run under Mypy.
-    from typing import Optional
-    from typing import Text
-    from typing import Dict
-    from typing import Tuple
-    from typing import List
-    from typing import Union
-    from typing import Type
-    from typing import Any
-    from typing import Sequence
-    from typing import Hashable
+    from typing import Any, Dict, Hashable, List, Optional, Sequence, Text, Tuple, Type, Union, cast
     from .manifest import Manifest
     Fuzzy = Dict[Optional[Tuple[Text, Text, Text]], List[int]]
     PageRanges = Dict[Text, List[int]]
@@ -31,14 +22,21 @@ class ManifestItemMeta(ABCMeta):
     attribute, and otherwise behaves like an ABCMeta."""
 
     def __new__(cls, name, bases, attrs):
-        # type: (Type[ManifestItemMeta], str, Tuple[ManifestItemMeta, ...], Dict[str, Any]) -> ManifestItemMeta
-        rv = super(ManifestItemMeta, cls).__new__(cls, name, bases, attrs)
-        if not isabstract(rv):
-            assert issubclass(rv, ManifestItem)
-            assert isinstance(rv.item_type, str)
-            item_types[rv.item_type] = rv
-
-        return rv  # type: ignore
+        # type: (Type[ManifestItemMeta], str, Tuple[type], Dict[str, Any]) -> ManifestItemMeta
+        inst = super(ManifestItemMeta, cls).__new__(cls, name, bases, attrs)
+        if isabstract(inst):
+            return inst
+
+        assert issubclass(inst, ManifestItem)
+        if MYPY:
+            inst_ = cast(Type[ManifestItem], inst)
+        else:
+            inst_ = inst
+
+        assert isinstance(inst_.item_type, str)
+        item_types[inst_.item_type] = inst_
+
+        return inst_
 
 
 class ManifestItem(metaclass=ManifestItemMeta):

tools/manifest/utils.py

@@ -1,6 +1,6 @@
 import os
-import platform
 import subprocess
+import sys
 
 MYPY = False
 if MYPY:
@@ -31,7 +31,7 @@ def rel_path_to_url(rel_path, url_base="/"):
 
 def from_os_path(path):
     # type: (Text) -> Text
-    assert os.path.sep == u"/" or platform.system() == "Windows"
+    assert os.path.sep == u"/" or sys.platform == "win32"
     if u"/" == os.path.sep:
         rv = path
     else:
@@ -43,7 +43,7 @@ def from_os_path(path):
 
 def to_os_path(path):
     # type: (Text) -> Text
-    assert os.path.sep == u"/" or platform.system() == "Windows"
+    assert os.path.sep == u"/" or sys.platform == "win32"
     if u"\\" in path:
         raise ValueError("normalised path contains \\")
     if u"/" == os.path.sep:
@@ -59,7 +59,7 @@ def gitfunc(cmd, *args):
         try:
             return subprocess.check_output(full_cmd, cwd=path, stderr=subprocess.STDOUT).decode('utf8')
         except Exception as e:
-            if platform.uname()[0] == "Windows" and isinstance(e, WindowsError):
+            if sys.platform == "win32" and isinstance(e, WindowsError):
                 full_cmd[0] = u"git.bat"
                 return subprocess.check_output(full_cmd, cwd=path, stderr=subprocess.STDOUT).decode('utf8')
             else:

tools/mypy.ini

@@ -22,6 +22,8 @@ warn_return_any = True
 warn_unused_configs = True
 warn_unused_ignores = True
 
+show_error_codes = True
+
 # Ignore missing or untyped libraries.
 
 [mypy-github.*]

tools/requirements_mypy.txt

@@ -1,3 +1,11 @@
 mypy==0.931
 mypy-extensions==0.4.3
+toml==0.10.2
 typed-ast==1.4.3
+types-atomicwrites==1.4.1
+types-PyYAML==6.0.0
+types-requests==2.25.11
+types-setuptools==57.4.2
+types-six==1.16.2
+types-ujson==4.2.0
+typing-extensions==3.10.0.2

tools/tox.ini

@@ -1,52 +1,24 @@
 [tox]
-envlist = py36,py37,py38,py39,{py36,py37,py38,py39}-flake8,{py36,py37,py38,py39}-mypy
+envlist = py36,py37,py38,py39,{py36,py37,py38,py39}-{flake8,mypy}
 skipsdist=True
-skip_missing_interpreters = False
+skip_missing_interpreters=False
 
 [testenv]
 deps =
-  -r{toxinidir}/requirements_pytest.txt
-  -r{toxinidir}/requirements_tests.txt
+  !flake8-!mypy: -r{toxinidir}/requirements_pytest.txt
+  !flake8-!mypy: -r{toxinidir}/requirements_tests.txt
+  flake8: -r{toxinidir}/requirements_flake8.txt
+  mypy: -r{toxinidir}/requirements_mypy.txt
 
-commands = pytest --cov=tools --cov-report=term {posargs}
+changedir =
+  mypy: {toxinidir}/..
+
+commands =
+  !flake8-!mypy: pytest --cov=tools --cov-report=term {posargs}
+  flake8: flake8 --append-config={toxinidir}/flake8.ini {posargs}
+  mypy: mypy --config-file={toxinidir}/mypy.ini tools/
 
 passenv =
   HYPOTHESIS_PROFILE
   PY_COLORS
   TASKCLUSTER_ROOT_URL
-
-[testenv:py36-flake8]
-deps = -rrequirements_flake8.txt
-commands = flake8 --append-config={toxinidir}/flake8.ini {posargs}
-
-[testenv:py37-flake8]
-deps = -rrequirements_flake8.txt
-commands = flake8 --append-config={toxinidir}/flake8.ini {posargs}
-
-[testenv:py38-flake8]
-deps = -rrequirements_flake8.txt
-commands = flake8 --append-config={toxinidir}/flake8.ini {posargs}
-
-[testenv:py39-flake8]
-deps = -rrequirements_flake8.txt
-commands = flake8 --append-config={toxinidir}/flake8.ini {posargs}
-
-[testenv:py36-mypy]
-deps = -rrequirements_mypy.txt
-changedir = {toxinidir}/..
-commands = mypy --config-file={toxinidir}/mypy.ini tools/
-
-[testenv:py37-mypy]
-deps = -rrequirements_mypy.txt
-changedir = {toxinidir}/..
-commands = mypy --config-file={toxinidir}/mypy.ini tools/
-
-[testenv:py38-mypy]
-deps = -rrequirements_mypy.txt
-changedir = {toxinidir}/..
-commands = mypy --config-file={toxinidir}/mypy.ini tools/
-
-[testenv:py39-mypy]
-deps = -rrequirements_mypy.txt
-changedir = {toxinidir}/..
-commands = mypy --config-file={toxinidir}/mypy.ini tools/