Bump requires-python to Python 3.8+

This enables the use of newer Python typing functionality without
compatibility shims.

Author: pradyunsg

pyproject.toml

@@ -8,7 +8,7 @@ authors = [
     {name = "Thomas Kluyver", email = "[email protected]"},
 ]
 readme = "README.rst"
-requires-python = ">=3.7"
+requires-python = ">=3.8"
 dependencies = []
 classifiers = [
     "License :: OSI Approved :: MIT License",

src/pyproject_hooks/_impl.py

@@ -6,24 +6,10 @@
 from os.path import abspath
 from os.path import join as pjoin
 from subprocess import STDOUT, check_call, check_output
-from typing import TYPE_CHECKING, Any, Dict, Iterator, List, Optional
+from typing import Any, Dict, Iterator, List, Optional, Protocol
 
 from ._in_process import _in_proc_script_path
 
-if TYPE_CHECKING:
-    from typing import Protocol
-
-    class SubprocessRunner(Protocol):
-        """A protocol for the subprocess runner."""
-
-        def __call__(
-            self,
-            cmd: List[str],
-            cwd: Optional[str] = None,
-            extra_environ: Optional[Dict[str, str]] = None,
-        ) -> None:
-            ...
-
 
 def write_json(obj: Dict[str, Any], path: str, **kwargs) -> None:
     with open(path, "w", encoding="utf-8") as f:
@@ -71,6 +57,18 @@ def __init__(self, traceback: str) -> None:
         self.traceback = traceback
 
 
+class SubprocessRunner(Protocol):
+    """A protocol for the subprocess runner."""
+
+    def __call__(
+        self,
+        cmd: List[str],
+        cwd: Optional[str] = None,
+        extra_environ: Optional[Dict[str, str]] = None,
+    ) -> None:
+        ...
+
+
 def default_subprocess_runner(
     cmd: List[str],
     cwd: Optional[str] = None,