bpo-40334: Allow to run make regen-pegen without distutils (GH-19684)

Author: pablogsal

Tools/peg_generator/pegen/__main__.py

@@ -11,11 +11,6 @@
 import token
 import traceback
 
-from typing import Final
-
-from pegen.build import build_parser_and_generator
-from pegen.testutil import print_memstats
-
 
 argparser = argparse.ArgumentParser(
     prog="pegen", description="Experimental PEG-like parser generator"
@@ -52,6 +47,9 @@
 
 
 def main() -> None:
+    from pegen.build import build_parser_and_generator
+    from pegen.testutil import print_memstats
+
     args = argparser.parse_args()
     verbose = args.verbose
     verbose_tokenizer = verbose >= 3
@@ -133,4 +131,7 @@ def main() -> None:
 
 
 if __name__ == "__main__":
+    if sys.version_info < (3, 8):
+        print("ERROR: using pegen requires at least Python 3.8!", file=sys.stderr)
+        sys.exit(1)
     main()

Tools/peg_generator/pegen/build.py

@@ -6,12 +6,6 @@
 
 from typing import Optional, Tuple
 
-import distutils.log
-from distutils.core import Distribution, Extension
-from distutils.command.clean import clean  # type: ignore
-from distutils.command.build_ext import build_ext  # type: ignore
-from distutils.tests.support import fixup_build_ext
-
 from pegen.c_generator import CParserGenerator
 from pegen.grammar import Grammar
 from pegen.grammar_parser import GeneratedParser as GrammarParser
@@ -47,6 +41,12 @@ def compile_c_extension(
     If *build_dir* is provided, that path will be used as the temporary build directory
     of distutils (this is useful in case you want to use a temporary directory).
     """
+    import distutils.log
+    from distutils.core import Distribution, Extension
+    from distutils.command.clean import clean  # type: ignore
+    from distutils.command.build_ext import build_ext  # type: ignore
+    from distutils.tests.support import fixup_build_ext
+
     if verbose:
         distutils.log.set_verbosity(distutils.log.DEBUG)