remove uses of "npm bin"

This was removed from recent Node versions. Using 'npx' is the new way
and should resolve this issue.

I suppose we might run into someone who had a non-working npx and it
breaks, but we'll cross that bridge when we come to it; it works in my
testing and there are people broken in the current version.

tzk/tw.py

@@ -7,20 +7,10 @@ import subprocess
 from textwrap import dedent
 from typing import Callable, Optional, Sequence
 
-from tzk import config
 from tzk import git
 from tzk.util import pushd
 
 
-@functools.lru_cache(1)
-def _npm_bin() -> str:
-    return subprocess.check_output(("npm", "bin"), text=True).strip()
-
-
-def _tw_path() -> str:
-    return _npm_bin() + "/tiddlywiki"
-
-
 @functools.lru_cache(1)
 def _whoami() -> str:
     "Try to guess the user's name."
@@ -47,9 +37,9 @@ def exec(args: Sequence[Sequence[str]], base_wiki_folder: str = None) -> int:
     # must pushd into base wiki to find the tiddlywiki node_modules
     if base_wiki_folder is not None:
         with pushd(base_wiki_folder):
-            call_args = [_tw_path()]
+            call_args = ["npx", "tiddlywiki"]
     else:
-        call_args = [_tw_path()]
+        call_args = ["npx", "tiddlywiki"]
 
     if base_wiki_folder is not None:
         call_args.append(base_wiki_folder)
@@ -114,7 +104,7 @@ def _init_tw(wiki_name: str) -> None:
         old_edition_path = os.environ.get('TIDDLYWIKI_EDITION_PATH')
         os.environ['TIDDLYWIKI_EDITION_PATH'] = str(Path(__file__).parent / "editions")
         try:
-            subprocess.check_call((_tw_path(), "--init", "tzk"))
+            subprocess.check_call(("npx", "tiddlywiki", "--init", "tzk"))
         finally:
             if old_edition_path:
                 os.environ['TIDDLYWIKI_EDITION_PATH'] = old_edition_path