Make Env an ABC (Abstract Base Class)

Env appears to be used as an ABC, yet uses an older Python
pattern: its abstract methods raise NotImplementedError().

Improve by making the class inherit from ABC, and use
@AbstractMethod to mark its abstract methods.

src/poetry/utils/env/base_env.py

@@ -7,6 +7,8 @@
 import sys
 import sysconfig
 
+from abc import ABC
+from abc import abstractmethod
 from functools import cached_property
 from pathlib import Path
 from subprocess import CalledProcessError
@@ -32,7 +34,7 @@
     PythonVersion = Tuple[int, int, int, str, int]
 
 
-class Env:
+class Env(ABC):
     """
     An abstract Python environment.
     """
@@ -223,8 +225,8 @@ def is_path_relative_to_lib(self, path: Path) -> bool:
         return False
 
     @property
-    def sys_path(self) -> list[str]:
-        raise NotImplementedError()
+    @abstractmethod
+    def sys_path(self) -> list[str]: ...
 
     @property
     def paths(self) -> dict[str, str]:
@@ -262,20 +264,20 @@ def get_base_prefix(cls) -> Path:
 
         return Path(sys.prefix)
 
-    def get_marker_env(self) -> dict[str, Any]:
-        raise NotImplementedError()
+    @abstractmethod
+    def get_marker_env(self) -> dict[str, Any]: ...
 
     def get_pip_command(self, embedded: bool = False) -> list[str]:
         if embedded or not Path(self._bin(self._pip_executable)).exists():
             return [str(self.python), str(self.pip_embedded)]
         # run as module so that pip can update itself on Windows
         return [str(self.python), "-m", "pip"]
 
-    def get_supported_tags(self) -> list[Tag]:
-        raise NotImplementedError()
+    @abstractmethod
+    def get_supported_tags(self) -> list[Tag]: ...
 
-    def get_paths(self) -> dict[str, str]:
-        raise NotImplementedError()
+    @abstractmethod
+    def get_paths(self) -> dict[str, str]: ...
 
     def is_valid_for_marker(self, marker: BaseMarker) -> bool:
         valid: bool = marker.validate(self.marker_env)
@@ -351,8 +353,8 @@ def execute(self, bin: str, *args: str, **kwargs: Any) -> int:
         exe.communicate()
         return exe.returncode
 
-    def is_venv(self) -> bool:
-        raise NotImplementedError()
+    @abstractmethod
+    def is_venv(self) -> bool: ...
 
     @property
     def script_dirs(self) -> list[Path]: