Use release instead of base_version

.github/workflows/publish.yml

@@ -60,7 +60,7 @@ jobs:
       - name: Get the latest release for this version from Test PyPI
         if: github.event_name == 'workflow_dispatch'
         run: |
-          curl https://test.pypi.org/pypi/backports-datetime-fromisoformat/json | python -c 'import json, sys; from packaging import version; contents=sys.stdin.read(); parsed = json.loads(contents); new_release_number = version.parse("${{ env.version_from_release_tag }}"); existing_releases = [version.parse(x) for x in parsed["releases"].keys()]; existing_pypi_version = max([x for x in existing_releases if x.base_version == new_release_number.base_version], default=version.parse("0.0.0")); print(f"test_pypi_version={existing_pypi_version}")' >> $GITHUB_ENV
+          curl https://test.pypi.org/pypi/backports-datetime-fromisoformat/json | python -c 'import json, sys; from packaging import version; contents=sys.stdin.read(); parsed = json.loads(contents); new_release_number = version.parse("${{ env.version_from_release_tag }}"); existing_releases = [version.parse(x) for x in parsed["releases"].keys()]; existing_pypi_version = max([x for x in existing_releases if x.release == new_release_number.release], default=version.parse("0.0.0")); print(f"test_pypi_version={existing_pypi_version}")' >> $GITHUB_ENV
 
       - name: Generate the developmental release version
         if: github.event_name == 'workflow_dispatch'
@@ -252,7 +252,7 @@ jobs:
       - name: Get the latest release for this version from Test PyPI
         if: github.event_name == 'workflow_dispatch'
         run: |
-          curl https://test.pypi.org/pypi/backports-datetime-fromisoformat/json | python -c 'import json, sys; from packaging import version; contents=sys.stdin.read(); parsed = json.loads(contents); new_release_number = version.parse("${{ env.version_to_use }}"); existing_releases = [version.parse(x) for x in parsed["releases"].keys()]; existing_pypi_version = max([x for x in existing_releases if x.base_version == new_release_number.base_version], default=version.parse("0.0.0")); print(f"test_pypi_version={existing_pypi_version}")' >> $GITHUB_ENV
+          curl https://test.pypi.org/pypi/backports-datetime-fromisoformat/json | python -c 'import json, sys; from packaging import version; contents=sys.stdin.read(); parsed = json.loads(contents); new_release_number = version.parse("${{ env.version_to_use }}"); existing_releases = [version.parse(x) for x in parsed["releases"].keys()]; existing_pypi_version = max([x for x in existing_releases if x.release == new_release_number.release], default=version.parse("0.0.0")); print(f"test_pypi_version={existing_pypi_version}")' >> $GITHUB_ENV
 
       - name: Get the latest version from PyPI
         run: |