[DEV-12949] Python 3.13 Compatibility (#349)

* Fix unconditional import missed by reduce base install size PR

* Replace `cgi.parse_header()` with `email.message.EmailMessage`

This makes `indico-client` compatible with Python 3.13, which removed
the deprecated `cgi` module.

https://docs.python.org/3/whatsnew/3.13.html#pep-594-remove-dead-batteries-from-the-standard-library

* Update readme and tox with supported Python versions

README.md

@@ -8,7 +8,7 @@
 
 ---
 
-Required: Python 3.6, 3.7, or 3.8
+Required: Python 3.9+
 
 From PyPI:
 

indico/http/serialization.py

@@ -1,15 +1,13 @@
 """
 Handles deserialization / decoding of responses
 """
-import cgi
 import gzip
 import io
 import json
 import logging
 import traceback
 from collections import defaultdict
-
-import msgpack
+from email.message import EmailMessage
 
 from indico.errors import IndicoDecodingError
 
@@ -23,7 +21,7 @@ def decompress(response):
 
 
 def deserialize(response, force_json=False, force_decompress=False):
-    content_type, params = cgi.parse_header(response.headers.get("Content-Type"))
+    content_type, params = parse_header(response.headers.get("Content-Type"))
 
     if force_decompress or content_type in ["application/x-gzip", "application/gzip"]:
         content = decompress(response)
@@ -45,7 +43,7 @@ def deserialize(response, force_json=False, force_decompress=False):
         )
 
 async def aio_deserialize(response, force_json=False, force_decompress=False):
-    content_type, params = cgi.parse_header(response.headers.get("Content-Type"))
+    content_type, params = parse_header(response.headers.get("Content-Type"))
     content = await response.read()
 
     if force_decompress or content_type in ["application/x-gzip", "application/gzip"]:
@@ -65,6 +63,11 @@ async def aio_deserialize(response, force_json=False, force_decompress=False):
             content_type, charset, content.decode("ascii", "ignore")
         )
 
+def parse_header(header: str) -> tuple[str, dict[str, str]]:
+    email = EmailMessage()
+    email["Content-Type"] = header
+    return email.get_content_type(), email["Content-Type"].params
+
 def raw_bytes(content, *args, **kwargs):
     return content
 

tox.Dockerfile

@@ -6,7 +6,7 @@ RUN DEBIAN_FRONTEND=noninteractive apt-get update && apt-get install -yqq apt-tr
 #deadsnakes holds old versions of python for ubuntu
 RUN DEBIAN_FRONTEND=noninteractive apt-get install -yqq software-properties-common && add-apt-repository ppa:deadsnakes/ppa
 
-RUN  DEBIAN_FRONTEND=noninteractive apt-get -yqq install  python3.7 python3.8 python3.9 python3.10 python3.11 python3.12 python3-pip
+RUN  DEBIAN_FRONTEND=noninteractive apt-get -yqq install python3.9 python3.10 python3.11 python3.12 python3.13 python3-pip
 
 RUN pip3 install tox==4.11.3
 

tox.ini

@@ -1,6 +1,6 @@
 # content of: tox.ini , put in same dir as setup.py
 [tox]
-envlist = py38,py39,py310,py311,py312
+envlist = py39,py310,py311,py312,py313
 
 [testenv]
 extras = all