Check _has_route *within* the test function (#3187)

Test selection occurs after collection, so if we're in an environment
where we don't want to make outbound network connections, defer the
check to after selection.

This was the aim of #3166, but it wasn't tested in an environment where
ConnectionError is raised.

test/__init__.py

@@ -10,6 +10,7 @@
 import typing
 import warnings
 from collections.abc import Sequence
+from functools import wraps
 from importlib.abc import Loader, MetaPathFinder
 from importlib.machinery import ModuleSpec
 from types import ModuleType, TracebackType
@@ -29,8 +30,6 @@
 except ImportError:
     zstd = None
 
-import functools
-
 from urllib3 import util
 from urllib3.connectionpool import ConnectionPool
 from urllib3.exceptions import HTTPWarning
@@ -181,6 +180,20 @@ def _has_route() -> bool:
             else:
                 raise
 
+    def _skip_if_no_route(f: _TestFuncT) -> _TestFuncT:
+        """Skip test exuction if network is unreachable"""
+
+        @wraps(f)
+        def wrapper(*args: typing.Any, **kwargs: typing.Any) -> typing.Any:
+            global _requires_network_has_route
+            if _requires_network_has_route is None:
+                _requires_network_has_route = _has_route()
+            if not _requires_network_has_route:
+                pytest.skip("Can't run the test because the network is unreachable")
+            return f(*args, **kwargs)
+
+        return typing.cast(_TestFuncT, wrapper)
+
     def _decorator_requires_internet(
         decorator: typing.Callable[[_TestFuncT], _TestFuncT]
     ) -> typing.Callable[[_TestFuncT], _TestFuncT]:
@@ -191,17 +204,7 @@ def wrapper(f: _TestFuncT) -> typing.Any:
 
         return wrapper
 
-    global _requires_network_has_route
-
-    if _requires_network_has_route is None:
-        _requires_network_has_route = _has_route()
-
-    return _decorator_requires_internet(
-        pytest.mark.skipif(
-            not _requires_network_has_route,
-            reason="Can't run the test because the network is unreachable",
-        )
-    )
+    return _decorator_requires_internet(_skip_if_no_route)
 
 
 def resolvesLocalhostFQDN() -> typing.Callable[[_TestFuncT], _TestFuncT]:
@@ -213,7 +216,7 @@ def resolvesLocalhostFQDN() -> typing.Callable[[_TestFuncT], _TestFuncT]:
 
 
 def withPyOpenSSL(test: typing.Callable[..., _RT]) -> typing.Callable[..., _RT]:
-    @functools.wraps(test)
+    @wraps(test)
     def wrapper(*args: typing.Any, **kwargs: typing.Any) -> _RT:
         if not pyopenssl:
             pytest.skip("pyopenssl not available, skipping test.")