Merge pull request #9 from cidrblock/feature_require_venv

Require a virtual env

src/pip4a/base.py

@@ -48,7 +48,7 @@ def _set_interpreter(  # noqa: PLR0912
         if venv:
             if not venv.exists():
                 if create:
-                    if not venv.relative_to(Path.cwd()):
+                    if not venv.is_relative_to(Path.cwd()):
                         err = "Virtual environment must relative to cwd to create it."
                         logger.critical(err)
                     msg = f"Creating virtual environment: {venv}"

src/pip4a/cli.py

@@ -4,6 +4,7 @@
 
 import logging
 import os
+import site
 
 from pathlib import Path
 from typing import TYPE_CHECKING
@@ -69,6 +70,13 @@ def ensure_isolated(self: Cli) -> None:
             err = f"Collections found in {usr_coll}"
             errors.append(err)
 
+        if "VIRTUAL_ENV" not in env_vars and not self.args.venv:
+            err = (
+                "Unable to install in user site packages directory:"
+                f" {site.getusersitepackages()}, please activate or specify a virtual environment"
+            )
+            errors.append(err)
+
         if errors:
             err = (
                 "The development environment is not isolated,"