Remove shutil.which backport - it was added in Python 3.3

build.py

@@ -29,10 +29,7 @@ import shlex
 import textwrap
 import warnings
 
-try:
-    from shutil import which
-except ImportError:
-    from buildtools.backports.shutil_which import which
+from shutil import which
 
 try:
     from setuptools.modified import newer, newer_group

buildtools/backports/shutil_which.py

@@ -1,78 +0,0 @@
-"""Backport of shutil.which from Python 3.5
-
-The function is included unmodified from Python stdlib 3.5.1,
-and is (C) Python
-"""
-from __future__ import absolute_import  # Import system's os, not backports.os.
-
-import os
-import sys
-
-__version__ = '3.5.1'
-
-def backport_which(cmd, mode=os.F_OK | os.X_OK, path=None):
-    """Given a command, mode, and a PATH string, return the path which
-    conforms to the given mode on the PATH, or None if there is no such
-    file.
-
-    `mode` defaults to os.F_OK | os.X_OK. `path` defaults to the result
-    of os.environ.get("PATH"), or can be overridden with a custom search
-    path.
-
-    """
-    # Check that a given file can be accessed with the correct mode.
-    # Additionally check that `file` is not a directory, as on Windows
-    # directories pass the os.access check.
-    def _access_check(fn, mode):
-        return (os.path.exists(fn) and os.access(fn, mode)
-                and not os.path.isdir(fn))
-
-    # If we're given a path with a directory part, look it up directly rather
-    # than referring to PATH directories. This includes checking relative to the
-    # current directory, e.g. ./script
-    if os.path.dirname(cmd):
-        if _access_check(cmd, mode):
-            return cmd
-        return None
-
-    if path is None:
-        path = os.environ.get("PATH", os.defpath)
-    if not path:
-        return None
-    path = path.split(os.pathsep)
-
-    if sys.platform == "win32":
-        # The current directory takes precedence on Windows.
-        if not os.curdir in path:
-            path.insert(0, os.curdir)
-
-        # PATHEXT is necessary to check on Windows.
-        pathext = os.environ.get("PATHEXT", "").split(os.pathsep)
-        # See if the given file matches any of the expected path extensions.
-        # This will allow us to short circuit when given "python.exe".
-        # If it does match, only test that one, otherwise we have to try
-        # others.
-        if any(cmd.lower().endswith(ext.lower()) for ext in pathext):
-            files = [cmd]
-        else:
-            files = [cmd + ext for ext in pathext]
-    else:
-        # On other platforms you don't have things like PATHEXT to tell you
-        # what file suffixes are executable, so just pass on cmd as-is.
-        files = [cmd]
-
-    seen = set()
-    for dir in path:
-        normdir = os.path.normcase(dir)
-        if not normdir in seen:
-            seen.add(normdir)
-            for thefile in files:
-                name = os.path.join(dir, thefile)
-                if _access_check(name, mode):
-                    return name
-    return None
-
-try:
-    from shutil import which
-except ImportError:
-    which = backport_which