Drop Python 3.5

cibuildwheel/windows.py

@@ -7,8 +7,6 @@ from pathlib import Path
 from typing import Dict, List, NamedTuple, Optional, Sequence, Set
 from zipfile import ZipFile
 
-import toml
-
 from .architecture import Architecture
 from .environment import ParsedEnvironment
 from .logger import log
@@ -219,34 +217,6 @@ def setup_python(
     return env
 
 
-def pep_518_cp35_workaround(package_dir: Path, env: Dict[str, str]) -> None:
-    """
-    Python 3.5 PEP 518 hack (see https://github.com/pypa/pip/issues/8392#issuecomment-639563494)
-    Basically, nuget's Python is an embedded Python distribution, which is not supported by pip.
-    Before version 3.6, there was no way to disable the "embedded" behavior, including the ignoring
-    of environment variables, including the ones pip uses to setup PEP 518 builds.
-
-    The fix here is as suggested in that issue; we manually setup the PEP 518 requirements. Since we
-    are in a fresh environment (except for pinned cibuildweel dependencies), the build is already
-    mostly "isolated".
-    """
-
-    pyproject_path = package_dir / "pyproject.toml"
-
-    if pyproject_path.exists():
-        data = toml.load(pyproject_path)
-        requirements = data["build-system"].get("requires", []) if "build-system" in data else []
-
-        if requirements:
-            log.step("Performing PEP518 workaround...")
-            with tempfile.TemporaryDirectory() as d:
-                reqfile = Path(d) / "requirements.txt"
-                with reqfile.open("w") as f:
-                    for r in requirements:
-                        print(r, file=f)
-                call(["pip", "install", "-r", reqfile], env=env)
-
-
 def build(options: BuildOptions) -> None:
     temp_dir = Path(tempfile.mkdtemp(prefix="cibuildwheel"))
     built_wheel_dir = temp_dir / "built_wheel"
@@ -286,11 +256,6 @@ def build(options: BuildOptions) -> None:
                 )
                 shell(before_build_prepared, env=env)
 
-            # activate the PEP 518 patch if on Windows Python 3.5
-            # (will only have an effect if PEP 517 builds are used):
-            if config.version.startswith("3.5"):
-                pep_518_cp35_workaround(options.package_dir, env)
-
             log.step("Building wheel...")
             if built_wheel_dir.exists():
                 shutil.rmtree(built_wheel_dir)