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stbi/Lib/site-packages/pip/_internal/utils/virtualenv.py

+from __future__ import absolute_import
+
+import logging
+import os
+import re
+import site
+import sys
+
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+
+if MYPY_CHECK_RUNNING:
+    from typing import List, Optional
+
+logger = logging.getLogger(__name__)
+_INCLUDE_SYSTEM_SITE_PACKAGES_REGEX = re.compile(
+    r"include-system-site-packages\s*=\s*(?P<value>true|false)"
+)
+
+
+def _running_under_venv():
+    # type: () -> bool
+    """Checks if sys.base_prefix and sys.prefix match.
+
+    This handles PEP 405 compliant virtual environments.
+    """
+    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
+
+    Returns None, if it could not read/access the file.
+    """
+    pyvenv_cfg_file = os.path.join(sys.prefix, 'pyvenv.cfg')
+    try:
+        with open(pyvenv_cfg_file) as f:
+            return f.read().splitlines()  # avoids trailing newlines
+    except IOError:
+        return None
+
+
+def _no_global_under_venv():
+    # type: () -> bool
+    """Check `{sys.prefix}/pyvenv.cfg` for system site-packages inclusion
+
+    PEP 405 specifies that when system site-packages are not supposed to be
+    visible from a virtual environment, `pyvenv.cfg` must contain the following
+    line:
+
+        include-system-site-packages = false
+
+    Additionally, log a warning if accessing the file fails.
+    """
+    cfg_lines = _get_pyvenv_cfg_lines()
+    if cfg_lines is None:
+        # We're not in a "sane" venv, so assume there is no system
+        # site-packages access (since that's PEP 405's default state).
+        logger.warning(
+            "Could not access 'pyvenv.cfg' despite a virtual environment "
+            "being active. Assuming global site-packages is not accessible "
+            "in this environment."
+        )
+        return True
+
+    for line in cfg_lines:
+        match = _INCLUDE_SYSTEM_SITE_PACKAGES_REGEX.match(line)
+        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.
+    """
+    # PEP 405 compliance needs to be checked first since virtualenv >=20 would
+    # return True for both checks, but is only able to use the PEP 405 config.
+    if _running_under_venv():
+        return _no_global_under_venv()
+
+    if _running_under_regular_virtualenv():
+        return _no_global_under_regular_virtualenv()
+
+    return False