Make sure sys._base_executable is sane in Vim plugin (#1380)

The `venv` module relies on `sys._base_executable` to determine the
Python executable to run, but with recent versions of Vim, this is set
to the `vim` executable. A possible workaround is to just override it,
since the `black` plugin already overrides `sys.executable` (possibly
for similar reasons?) anyway.

diff --git a/plugin/black.vim b/plugin/black.vim
index 9978e6c0667d9b22a9ee4046c4c59ed82ec710bc..f3e4409c13a2bd8bc1d1693ce16fdbdb66cfcf6b 100644 (file)
--- a/plugin/black.vim
+++ b/plugin/black.vim
@@ -110,13 +110,23 @@ def _initialize_black_env(upgrade=False):
   if not virtualenv_path.is_dir():
     print('Please wait, one time setup for Black.')
     _executable = sys.executable
+    _base_executable = getattr(sys, "_base_executable", _executable)
     try:
-      sys.executable = str(_get_python_binary(Path(sys.exec_prefix)))
+      executable = str(_get_python_binary(Path(sys.exec_prefix)))
+      sys.executable = executable
+      sys._base_executable = executable
       print(f'Creating a virtualenv in {virtualenv_path}...')
       print('(this path can be customized in .vimrc by setting g:black_virtualenv)')
       venv.create(virtualenv_path, with_pip=True)
+    except Exception:
+      print('Encountered exception while creating virtualenv (see traceback below).')
+      print(f'Removing {virtualenv_path}...')
+      import shutil
+      shutil.rmtree(virtualenv_path)
+      raise
     finally:
       sys.executable = _executable
+      sys._base_executable = _base_executable
     first_install = True
   if first_install:
     print('Installing Black with pip...')