Replace distutils.spawn.find_executable with shutil.which

The distutils.spawn.find_executable function is not available on stock system
Python 3 in recent Debian-based distributions. Since shutil.which is a better
alternative but not available on Python 2.7, we include a copy of that function
and use it in place of find_executable.

jedi/_compatibility.py

@@ -513,3 +513,67 @@ class GeneralizedPopen(subprocess.Popen):
                 CREATE_NO_WINDOW = 0x08000000
             kwargs['creationflags'] = CREATE_NO_WINDOW
         super(GeneralizedPopen, self).__init__(*args, **kwargs)
+
+
+# shutil.which is not available on Python 2.7.
+def 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

jedi/api/environment.py

@@ -9,11 +9,8 @@ import hashlib
 import filecmp
 from subprocess import PIPE
 from collections import namedtuple
-# When dropping Python 2.7 support we should consider switching to
-# `shutil.which`.
-from distutils.spawn import find_executable
 
-from jedi._compatibility import GeneralizedPopen
+from jedi._compatibility import GeneralizedPopen, which
 from jedi.cache import memoize_method, time_cache
 from jedi.evaluate.compiled.subprocess import get_subprocess, \
     EvaluatorSameProcess, EvaluatorSubprocess
@@ -276,7 +273,7 @@ def get_system_environment(version):
     :raises: :exc:`.InvalidPythonEnvironment`
     :returns: :class:`Environment`
     """
-    exe = find_executable('python' + version)
+    exe = which('python' + version)
     if exe:
         if exe == sys.executable:
             return SameEnvironment()