Migrate virtualenv detection to PEP 405

src/pip/_internal/utils/virtualenv.py

@@ -3,7 +3,6 @@
 import logging
 import os
 import re
-import site
 import sys
 
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
@@ -17,7 +16,7 @@
 )
 
 
-def _running_under_venv():
+def running_under_virtualenv():
     # type: () -> bool
     """Checks if sys.base_prefix and sys.prefix match.
 
@@ -26,23 +25,6 @@ def _running_under_venv():
     return sys.prefix != getattr(sys, "base_prefix", sys.prefix)
 
 
-def _running_under_regular_virtualenv():
-    # type: () -> bool
-    """Checks if sys.real_prefix is set.
-
-    This handles virtual environments created with pypa's virtualenv.
-    """
-    # pypa/virtualenv case
-    return hasattr(sys, 'real_prefix')
-
-
-def running_under_virtualenv():
-    # type: () -> bool
-    """Return True if we're running inside a virtualenv, False otherwise.
-    """
-    return _running_under_venv() or _running_under_regular_virtualenv()
-
-
 def _get_pyvenv_cfg_lines():
     # type: () -> Optional[List[str]]
     """Reads {sys.prefix}/pyvenv.cfg and returns its contents as list of lines
@@ -57,7 +39,7 @@ def _get_pyvenv_cfg_lines():
         return None
 
 
-def _no_global_under_venv():
+def virtualenv_no_global():
     # type: () -> bool
     """Check `{sys.prefix}/pyvenv.cfg` for system site-packages inclusion
 
@@ -85,31 +67,3 @@ def _no_global_under_venv():
         if match is not None and match.group('value') == 'false':
             return True
     return False
-
-
-def _no_global_under_regular_virtualenv():
-    # type: () -> bool
-    """Check if "no-global-site-packages.txt" exists beside site.py
-
-    This mirrors logic in pypa/virtualenv for determining whether system
-    site-packages are visible in the virtual environment.
-    """
-    site_mod_dir = os.path.dirname(os.path.abspath(site.__file__))
-    no_global_site_packages_file = os.path.join(
-        site_mod_dir, 'no-global-site-packages.txt',
-    )
-    return os.path.exists(no_global_site_packages_file)
-
-
-def virtualenv_no_global():
-    # type: () -> bool
-    """Returns a boolean, whether running in venv with no system site-packages.
-    """
-
-    if _running_under_regular_virtualenv():
-        return _no_global_under_regular_virtualenv()
-
-    if _running_under_venv():
-        return _no_global_under_venv()
-
-    return False