Improve GitHub release workflow

This changes the existing script to just generate the release notes and delegate the actual publishing to the `softprops/action-gh-release@v1` action.

This allows us to delete the custom code, which failed recently in https://github.com/pytest-dev/pytest/actions/runs/7370258570/job/20056477756.

scripts/generate-gh-release-notes.py

@@ -0,0 +1,75 @@
+# mypy:disallow-untyped-defs
+"""
+Script used to publish GitHub release notes extracted from CHANGELOG.rst.
+
+This script is meant to be executed after a successful deployment in GitHub actions.
+
+Uses the following environment variables:
+
+* GIT_TAG: the name of the tag of the current commit.
+* GH_RELEASE_NOTES_TOKEN: a personal access token with 'repo' permissions.
+
+  Create one at:
+
+    https://github.com/settings/tokens
+
+  This token should be set in a secret in the repository, which is exposed as an
+  environment variable in the main.yml workflow file.
+
+The script also requires ``pandoc`` to be previously installed in the system.
+
+Requires Python3.6+.
+"""
+import re
+import sys
+from pathlib import Path
+
+import pypandoc
+
+
+def parse_changelog(tag_name):
+    p = Path(__file__).parent.parent / "doc/en/changelog.rst"
+    changelog_lines = p.read_text(encoding="UTF-8").splitlines()
+
+    title_regex = re.compile(r"pytest (\d\.\d+\.\d+\w*) \(\d{4}-\d{2}-\d{2}\)")
+    consuming_version = False
+    version_lines = []
+    for line in changelog_lines:
+        m = title_regex.match(line)
+        if m:
+            # found the version we want: start to consume lines until we find the next version title
+            if m.group(1) == tag_name:
+                consuming_version = True
+            # found a new version title while parsing the version we want: break out
+            elif consuming_version:
+                break
+        if consuming_version:
+            version_lines.append(line)
+
+    return "\n".join(version_lines)
+
+
+def convert_rst_to_md(text):
+    return pypandoc.convert_text(
+        text, "md", format="rst", extra_args=["--wrap=preserve"]
+    )
+
+
+def main(argv):
+    if len(argv) != 3:
+        print("Usage: generate-gh-release-notes VERSION FILE")
+        return 2
+
+    version, filename = argv[1:3]
+    print(f"Generating GitHub release notes for version {version}")
+    rst_body = parse_changelog(version)
+    md_body = convert_rst_to_md(rst_body)
+    Path(filename).write_text(md_body, encoding="UTF-8")
+    print()
+    print(f"Done: {filename}")
+    print()
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv))