Fix pip_cert pytest fixture (#2083)

pip_cert is recognized as a generator so it should not use
return if PIP_CERT is in os.environ.

Fixes: #2048

tests/conftest.py

@@ -153,14 +153,15 @@ def pip_cert(tmp_path_factory):
  # workaround for https:/pypa/pip/issues/8984 - if the certificate is explicitly set no error can happen
  key = ensure_str("PIP_CERT")
  if key in os.environ:
- return
- cert = tmp_path_factory.mktemp("folder") / "cert"
- import pkgutil
-
- cert_data = pkgutil.get_data("pip._vendor.certifi", "cacert.pem")
- cert.write_bytes(cert_data)
- with change_os_environ(key, str(cert)):
  yield
+ else:
+ cert = tmp_path_factory.mktemp("folder") / "cert"
+ import pkgutil
+
+ cert_data = pkgutil.get_data("pip._vendor.certifi", "cacert.pem")
+ cert.write_bytes(cert_data)
+ with change_os_environ(key, str(cert)):
+ yield
 
 
 @pytest.fixture(autouse=True)