Bail out of the release if twine fails

Before (scripts-dev/release.py --help):

```
  Requirements:   - The dev dependencies be installed, which can be done via:

          pip install -e .[dev]

    - A checkout of the sytest repository at ../sytest

  Then to use:

      ./scripts-dev/release.py prepare

      # ... ask others to look at the changelog ...

      ./scripts-dev/release.py tag

      # wait for assets to build, either manually or with:     ./scripts-
      dev/release.py wait-for-actions

      ./scripts-dev/release.py publish

      ./scripts-dev/release.py upload

      ./scripts-dev/release.py merge-back

      # Optional: generate some nice links for the announcement     ./scripts-
      dev/release.py announce

```

After:

```
  Requirements:

    - The dev dependencies be installed, which can be done via:

          pip install -e .[dev]

    - A checkout of the sytest repository at ../sytest

  Then to use:

      ./scripts-dev/release.py prepare

      # ... ask others to look at the changelog ...

      ./scripts-dev/release.py tag

      # wait for assets to build, either manually or with:

      ./scripts-dev/release.py wait-for-actions

      ./scripts-dev/release.py publish

      ./scripts-dev/release.py upload

      ./scripts-dev/release.py merge-back

      # Optional: generate some nice links for the announcement

      ./scripts-dev/release.py announce
```

scripts-dev/release.py

@@ -58,6 +58,7 @@ def cli() -> None:
     """An interactive script to walk through the parts of creating a release.
 
     Requirements:
+
       - The dev dependencies be installed, which can be done via:
 
             pip install -e .[dev]
@@ -73,6 +74,7 @@ def cli() -> None:
         ./scripts-dev/release.py tag
 
         # wait for assets to build, either manually or with:
+
         ./scripts-dev/release.py wait-for-actions
 
         ./scripts-dev/release.py publish
@@ -82,6 +84,7 @@ def cli() -> None:
         ./scripts-dev/release.py merge-back
 
         # Optional: generate some nice links for the announcement
+
         ./scripts-dev/release.py announce
 
     Alternatively, `./scripts-dev/release.py full` will do all the above
@@ -482,7 +485,7 @@ def _upload(gh_token: Optional[str]) -> None:
             urllib.request.urlretrieve(asset_download_url, filename=filename)
 
         if click.confirm("Upload to PyPI?", default=True):
-            subprocess.run("twine upload *", shell=True, cwd=tmpdir)
+            subprocess.run("twine upload *", shell=True, cwd=tmpdir, check=True)
 
     click.echo(
         f"Done! Remember to merge the tag {tag_name} into the appropriate branches"