Adds ext.drivers.venv and modifies .gitignore to allow it to be added

.gitignore

@@ -1,7 +1,7 @@
 build
 dist
 *egg-info
-venv
+.venv
 docs/site
 __pycache__
 *~

src/venv_management/ext/drivers/venv/__init__.py

@@ -0,0 +1 @@
+from .driver import VEnvDriver as Driver

src/venv_management/ext/drivers/venv/driver.py

@@ -0,0 +1,89 @@
+import logging
+import os
+import shutil
+import subprocess
+import sys
+from pathlib import Path
+from typing import Optional, List
+
+from venv_management import PythonNotFound
+from venv_management.driver import Driver
+
+logger = logging.getLogger(__name__)
+
+DEFAULT_VENVS_DIRPATH = Path.home() / ".virtualenvs"
+
+
+class VEnvDriver(Driver):
+    """A driver using the Python Standard Library venv module.
+
+    This driver expects manages virtual environments in either the directory pointed to by $WORKON_HOME
+    or, if the former is not defined, $HOME/.virtualenvs. If necessary, the virtual environment directory
+    will be created.
+    """
+    def __init__(self, name: str):
+        super().__init__(name)
+        workon_home_dirpath = os.environ.get("WORKON_HOME")
+        self._venvs_dirpath = Path(
+            os.path.expandvars(workon_home_dirpath)
+            if workon_home_dirpath else
+            DEFAULT_VENVS_DIRPATH
+        ).expanduser()
+
+    def _check_availability(self):
+        import venv
+        self._venv_module = venv
+
+    def list_virtual_envs(self) -> List[str]:
+        if not self._venvs_dirpath.is_dir():
+            if self._venvs_dirpath.exists():
+                raise RuntimeError(f"The virtual environment directory {self._venvs_dirpath} is not a directory")
+            return []
+        return [
+            subdir.name
+            for subdir in self._venvs_dirpath.iterdir()
+            if subdir.is_dir() and (subdir / "pyvenv.cfg").is_file()
+        ]
+
+    def make_virtual_env(self, name, *, python=None, project_path=None, packages=None, requirements_file=None,
+                         system_site_packages=False, pip=True, setuptools=True, wheel=True) -> Optional[Path]:
+        if not self._venvs_dirpath.is_dir():
+            if self._venvs_dirpath.exists():
+                raise RuntimeError(f"The virtual environment directory {self._venvs_dirpath} is not a directory")
+            self._venvs_dirpath.mkdir(parents=True, exist_ok=True)
+
+        virtualenv_dirpath = self._venvs_dirpath / name
+        python_exe = Path(python or sys.executable)
+
+        if not python_exe.is_file():
+            raise PythonNotFound(f"Could not locate Python {python}")
+
+        command = [python_exe, "-m", "venv", virtualenv_dirpath]
+
+        if system_site_packages:
+            command.append("--system-site-packages")
+
+        if not pip:
+            command.append("--without-pip")
+
+        if pip:
+            command.append("--upgrade-deps")
+
+        if project_path is not None:
+            raise ValueError(f"Project path not supported for {self.name!r} driver")
+
+        # TODO: setuptools, wheel, requirements_file, packages
+
+        subprocess.run(command, check=True)
+        return virtualenv_dirpath
+
+    def remove_virtual_env(self, name: str):
+        path = self.resolve_virtual_env(name)
+        shutil.rmtree(path)
+
+    def resolve_virtual_env(self, name: str) -> Path:
+        if not name:
+            raise ValueError("The name passed to resolve_virtual_env cannot be empty")
+        if name not in self.list_virtual_envs():
+            raise ValueError(f"No virtual environment called {name!r}")
+        return self._venvs_dirpath / name