Skip all failing tests when using venv

Our isolation logic for venv isn't correct and that is causing these
tests to fail. The culprits for this are:

  tests/lib/venv.py::VirtualEnvironment.user_site_packages
  tests/lib/venv.py::VirtualEnvironment.sitecustomize

Both these together are supposed to create an environment to isolate the
tests. However, they were written for virtualenv and make assumptions
that are not true for environments created with venv. Until we can fix
VirtualEnvironment to properly isolate the test from the underlying test
environment when using venv, these tests will continue to fail.

This is blocking an important bugfix for users facing issues with since
pip is installing packages into `--user` when run in a venv, even when
`--user` isn't visible from that environment.

As a temporary band-aid for this problem, I'm skipping these tests to
unblock us from shipping the bugfix for the aforementioned issue.

The test isolation logic should be fixed to work for venv. Once such a
fix is made, this commit should be reverted.

tests/functional/test_freeze.py

@@ -703,6 +703,7 @@ def test_freeze_with_requirement_option_package_repeated_multi_file(script):
 
 
 @pytest.mark.network
+@pytest.mark.incompatible_with_test_venv
 def test_freeze_user(script, virtualenv, data):
     """
     Testing freeze with --user, first we have to install some stuff.
@@ -733,6 +734,7 @@ def test_freeze_path(tmpdir, script, data):
     _check_output(result.stdout, expected)
 
 
+@pytest.mark.incompatible_with_test_venv
 def test_freeze_path_exclude_user(tmpdir, script, data):
     """
     Test freeze with --path and make sure packages from --user are not picked

tests/functional/test_install.py

@@ -124,6 +124,7 @@ def test_pep518_allows_missing_requires(script, data, common_wheels):
     assert result.files_created
 
 
+@pytest.mark.incompatible_with_test_venv
 def test_pep518_with_user_pip(script, pip_src, data, common_wheels):
     """
     Check that build dependencies are installed into the build

tests/functional/test_install_reqs.py

@@ -227,6 +227,7 @@ def test_install_local_with_subdirectory(script):
     result.assert_installed('version_subpkg.py', editable=False)
 
 
+@pytest.mark.incompatible_with_test_venv
 def test_wheel_user_with_prefix_in_pydistutils_cfg(
         script, data, with_wheel):
     if os.name == 'posix':

tests/functional/test_install_user.py

@@ -27,6 +27,7 @@ def dist_in_site_packages(dist):
 class Tests_UserSite:
 
     @pytest.mark.network
+    @pytest.mark.incompatible_with_test_venv
     def test_reset_env_system_site_packages_usersite(self, script):
         """
         Check user site works as expected.
@@ -42,6 +43,7 @@ def test_reset_env_system_site_packages_usersite(self, script):
 
     @pytest.mark.network
     @need_svn
+    @pytest.mark.incompatible_with_test_venv
     def test_install_subversion_usersite_editable_with_distribute(
             self, script, tmpdir):
         """
@@ -55,6 +57,7 @@ def test_install_subversion_usersite_editable_with_distribute(
         )
         result.assert_installed('INITools', use_user_site=True)
 
+    @pytest.mark.incompatible_with_test_venv
     def test_install_from_current_directory_into_usersite(
             self, script, data, with_wheel):
         """
@@ -75,7 +78,6 @@ def test_install_from_current_directory_into_usersite(
         )
         assert dist_info_folder in result.files_created
 
-    @pytest.mark.incompatible_with_test_venv
     def test_install_user_venv_nositepkgs_fails(self, virtualenv,
                                                 script, data):
         """
@@ -96,6 +98,7 @@ def test_install_user_venv_nositepkgs_fails(self, virtualenv,
         )
 
     @pytest.mark.network
+    @pytest.mark.incompatible_with_test_venv
     def test_install_user_conflict_in_usersite(self, script):
         """
         Test user install with conflict in usersite updates usersite.
@@ -119,6 +122,7 @@ def test_install_user_conflict_in_usersite(self, script):
         assert not isfile(initools_v3_file), initools_v3_file
 
     @pytest.mark.network
+    @pytest.mark.incompatible_with_test_venv
     def test_install_user_conflict_in_globalsite(self, virtualenv, script):
         """
         Test user install with conflict in global site ignores site and
@@ -149,6 +153,7 @@ def test_install_user_conflict_in_globalsite(self, virtualenv, script):
         assert isdir(initools_folder)
 
     @pytest.mark.network
+    @pytest.mark.incompatible_with_test_venv
     def test_upgrade_user_conflict_in_globalsite(self, virtualenv, script):
         """
         Test user install/upgrade with conflict in global site ignores site and
@@ -178,6 +183,7 @@ def test_upgrade_user_conflict_in_globalsite(self, virtualenv, script):
         assert isdir(initools_folder)
 
     @pytest.mark.network
+    @pytest.mark.incompatible_with_test_venv
     def test_install_user_conflict_in_globalsite_and_usersite(
             self, virtualenv, script):
         """
@@ -214,6 +220,7 @@ def test_install_user_conflict_in_globalsite_and_usersite(
         assert isdir(initools_folder)
 
     @pytest.mark.network
+    @pytest.mark.incompatible_with_test_venv
     def test_install_user_in_global_virtualenv_with_conflict_fails(
             self, script):
         """

tests/functional/test_install_wheel.py

@@ -233,6 +233,7 @@ def test_wheel_record_lines_in_deterministic_order(script, data):
     assert record_lines == sorted(record_lines)
 
 
+@pytest.mark.incompatible_with_test_venv
 def test_install_user_wheel(script, data, with_wheel):
     """
     Test user install from wheel (that has a script)

tests/functional/test_list.py

@@ -94,6 +94,7 @@ def test_local_columns_flag(simple_script):
 
 
 @pytest.mark.network
+@pytest.mark.incompatible_with_test_venv
 def test_user_flag(script, data):
     """
     Test the behavior of --user flag in the list command
@@ -110,6 +111,7 @@ def test_user_flag(script, data):
 
 
 @pytest.mark.network
+@pytest.mark.incompatible_with_test_venv
 def test_user_columns_flag(script, data):
     """
     Test the behavior of --user --format=columns flags in the list command
@@ -502,6 +504,7 @@ def test_list_path(tmpdir, script, data):
     assert {'name': 'simple', 'version': '2.0'} in json_result
 
 
+@pytest.mark.incompatible_with_test_venv
 def test_list_path_exclude_user(tmpdir, script, data):
     """
     Test list with --path and make sure packages from --user are not picked

tests/functional/test_uninstall_user.py

@@ -9,6 +9,7 @@
 from tests.lib import assert_all_changes, pyversion
 
 
+@pytest.mark.incompatible_with_test_venv
 class Tests_UninstallUserSite:
 
     @pytest.mark.network