Specify Python exec path with minor version if available (psf#3507)

autoload/black.vim

@@ -43,7 +43,15 @@ def _get_python_binary(exec_prefix, pyver):
     return default
   if sys.platform[:3] == "win":
     return exec_prefix / 'python.exe'
-  return exec_prefix / 'bin' / f'python{pyver[0]}.{pyver[1]}'
+  bin_path = exec_prefix / "bin"
+  exec_path = (bin_path / f"python{pyver[0]}.{pyver[1]}").resolve()
+  if exec_path.exists():
+    return exec_path
+  # It is possible that some environments may only have python3
+  exec_path = (bin_path / f"python3").resolve()
+  if exec_path.exists():
+    return exec_path
+  raise ValueError("python executable not found")
 
 def _get_pip(venv_path):
   if sys.platform[:3] == "win":