Use httpcore PR

httpx/_models.py

@@ -3,8 +3,8 @@ import email.message
 import json as jsonlib
 import typing
 import urllib.request
-from contextlib import aclosing
 from collections.abc import Mapping
+from contextlib import aclosing
 from http.cookiejar import Cookie, CookieJar
 
 from ._content import ByteStream, UnattachedStream, encode_request, encode_response

pyproject.toml

@@ -29,7 +29,7 @@ classifiers = [
 ]
 dependencies = [
     "certifi",
-    "httpcore>=0.15.0,<0.17.0",
+    "httpcore==git+https://github.com/encode/httpcore.git@bug/async-early-stream-break",
     "idna",
     "sniffio",
 ]