test against python3.9

.github/workflows/python.yml

@@ -39,6 +39,7 @@ jobs:
         - '3.6'
         - '3.7'
         - '3.8'
+        - '3.9'
       fail-fast: false
     steps:
     - uses: actions/checkout@v2.4.0

pubmed_bibtex/__init__.py

@@ -71,7 +71,7 @@ class _TeXMedHtmlParser(html.parser.HTMLParser):
 def bibtex_entry_from_pmid(pmid: str) -> typing.Optional[str]:
     assert pmid.isdigit(), pmid
     resp = requests.get(_TEXMED_URL_PATTERN.format(pmid=pmid))
-    resp.raise_for_status()
+    resp.raise_for_status()  # raises requests.exceptions.HTTPError
     parser = _TeXMedHtmlParser()
     parser.feed(resp.text)
     return parser.bibtex_entry

setup.py

@@ -40,6 +40,7 @@ setuptools.setup(
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
         "Topic :: Scientific/Engineering :: Medical Science Apps.",
         "Topic :: Utilities",
     ],