Fix mypy checks on Windows

Previously we were making unguarded calls to non-Windows-only APIs. Mypy
only automatically excludes these from platform-specific checks when
inside conditions.

src/pip/_internal/utils/compat.py

@@ -257,12 +257,13 @@ else:
             return cr
         cr = ioctl_GWINSZ(0) or ioctl_GWINSZ(1) or ioctl_GWINSZ(2)
         if not cr:
-            try:
-                fd = os.open(os.ctermid(), os.O_RDONLY)
-                cr = ioctl_GWINSZ(fd)
-                os.close(fd)
-            except Exception:
-                pass
+            if sys.platform != "win32":
+                try:
+                    fd = os.open(os.ctermid(), os.O_RDONLY)
+                    cr = ioctl_GWINSZ(fd)
+                    os.close(fd)
+                except Exception:
+                    pass
         if not cr:
             cr = (os.environ.get('LINES', 25), os.environ.get('COLUMNS', 80))
         return int(cr[1]), int(cr[0])

src/pip/_internal/utils/filesystem.py

@@ -4,6 +4,7 @@ import os.path
 import random
 import shutil
 import stat
+import sys
 from contextlib import contextmanager
 from tempfile import NamedTemporaryFile
 
@@ -29,7 +30,7 @@ def check_path_owner(path):
     # type: (str) -> bool
     # If we don't have a way to check the effective uid of this process, then
     # we'll just assume that we own the directory.
-    if not hasattr(os, "geteuid"):
+    if sys.platform == "win32" or not hasattr(os, "geteuid"):
         return True
 
     previous = None

src/pip/_internal/utils/glibc.py

@@ -5,6 +5,7 @@ from __future__ import absolute_import
 
 import os
 import re
+import sys
 import warnings
 
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
@@ -26,6 +27,8 @@ def glibc_version_string_confstr():
     # to be broken or missing. This strategy is used in the standard library
     # platform module:
     # https://github.com/python/cpython/blob/fcf1d003bf4f0100c9d0921ff3d70e1127ca1b71/Lib/platform.py#L175-L183
+    if sys.platform == "win32":
+        return None
     try:
         # os.confstr("CS_GNU_LIBC_VERSION") returns a string like "glibc 2.17":
         _, version = os.confstr("CS_GNU_LIBC_VERSION").split()

tests/unit/test_utils.py

@@ -570,12 +570,14 @@ class TestGlibc(object):
                     # Didn't find the warning we were expecting
                     assert False
 
+    @pytest.mark.skipif("sys.platform == 'win32'")
     def test_glibc_version_string(self, monkeypatch):
         monkeypatch.setattr(
             os, "confstr", lambda x: "glibc 2.20", raising=False,
         )
         assert glibc_version_string() == "2.20"
 
+    @pytest.mark.skipif("sys.platform == 'win32'")
     def test_glibc_version_string_confstr(self, monkeypatch):
         monkeypatch.setattr(
             os, "confstr", lambda x: "glibc 2.20", raising=False,