setup: Drop support for python 3.7

The main reason to drop this version before it reaches its EOL is so
that we can begin to use unittest.IsolatedAsyncioTestCase to replace
deprecated portions of the tornado.testing module.

A secondary reason is that Python 3.8 introduced support for the
samesite cookie attribute, which allows us to deprecate the
xsrf_token mechanism.

.github/workflows/test.yml

@@ -36,8 +36,6 @@ jobs:
     strategy:
       matrix:
         include:
-          - python: '3.7'
-            tox_env: py37-full
           - python: '3.8'
             tox_env: py38-full
           - python: '3.9'

docs/index.rst

@@ -100,7 +100,7 @@ installed in this way, so you may wish to download a copy of the
 source tarball or clone the `git repository
 <https://github.com/tornadoweb/tornado>`_ as well.
 
-**Prerequisites**: Tornado 6.2 requires Python 3.7 or newer. The following
+**Prerequisites**: Tornado 6.3 requires Python 3.8 or newer. The following
 optional packages may be useful:
 
 * `pycurl <http://pycurl.io/>`_ is used by the optional

pyproject.toml

@@ -3,7 +3,7 @@ requires = ["setuptools", "wheel"]
 build-backend = "setuptools.build_meta"
 
 [tool.cibuildwheel]
-build = "cp3[789]* cp310* cp311*"
+build = "cp3[89]* cp310* cp311*"
 test-command = "python -m tornado.test"
 
 [tool.cibuildwheel.macos]

setup.cfg

@@ -2,7 +2,7 @@
 license_file = LICENSE
 
 [mypy]
-python_version = 3.7
+python_version = 3.8
 no_implicit_optional = True
 
 [mypy-tornado.*,tornado.platform.*]

setup.py

@@ -52,7 +52,7 @@ if (
             # Use the stable ABI so our wheels are compatible across python
             # versions.
             py_limited_api=True,
-            define_macros=[("Py_LIMITED_API", "0x03070000")],
+            define_macros=[("Py_LIMITED_API", "0x03080000")],
         )
     ]
 
@@ -63,7 +63,7 @@ if wheel is not None:
             python, abi, plat = super().get_tag()
 
             if python.startswith("cp"):
-                return "cp37", "abi3", plat
+                return "cp38", "abi3", plat
             return python, abi, plat
 
     kwargs["cmdclass"] = {"bdist_wheel": bdist_wheel_abi3}
@@ -72,7 +72,7 @@ if wheel is not None:
 setuptools.setup(
     name="tornado",
     version=version,
-    python_requires=">= 3.7",
+    python_requires=">= 3.8",
     packages=["tornado", "tornado.test", "tornado.platform"],
     package_data={
         # data files need to be listed both here (which determines what gets
@@ -112,7 +112,6 @@ setuptools.setup(
     classifiers=[
         "License :: OSI Approved :: Apache Software License",
         "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",

tox.ini

@@ -13,7 +13,7 @@
 [tox]
 envlist =
         # Basic configurations: Run the tests for each python version.
-        py37-full,py38-full,py39-full,py310-full,py311-full,pypy3-full
+        py38-full,py39-full,py310-full,py311-full,pypy3-full
 
         # Build and test the docs with sphinx.
         docs
@@ -27,7 +27,6 @@ whitelist_externals = /bin/sh
 [testenv]
 basepython =
            py3: python3
-           py37: python3.7
            py38: python3.8
            py39: python3.9
            py310: python3.10
@@ -51,7 +50,7 @@ deps =
 
 setenv =
        # Treat the extension as mandatory in testing (but not on pypy)
-       {py3,py37,py38,py39,py310,py311}: TORNADO_EXTENSION=1
+       {py3,py38,py39,py310,py311}: TORNADO_EXTENSION=1
        # CI workers are often overloaded and can cause our tests to exceed
        # the default timeout of 5s.
        ASYNC_TEST_TIMEOUT=25
@@ -63,7 +62,7 @@ setenv =
        # during sdist installation (and it doesn't seem to be
        # possible to set environment variables during that phase of
        # tox).
-       {py3,py37,py38,py39,py310,py311,pypy3}: PYTHONWARNINGS=error:::tornado
+       {py3,py38,py39,py310,py311,pypy3}: PYTHONWARNINGS=error:::tornado
 
 
 # All non-comment lines but the last must end in a backslash.