We no longer need to monkey-patch contextvars on 3.7+.

Fixes #1656

Also disable 32-bit manylinux builds because of https://github.com/cython/cython/issues/3840

.travis.yml

@@ -279,18 +279,20 @@ jobs:
         - mkdir -p $HOME/.cache/pip
         - chmod a+w $HOME/.cache/pip
 
-    - stage: test
-      name: 32-bit manylinux wheels (all Pythons)
-      language: python
-      services: docker
-      env: DOCKER_IMAGE=quay.io/pypa/manylinux2010_i686 PRE_CMD=linux32
-      install: docker pull $DOCKER_IMAGE
-      script: bash scripts/releases/make-manylinux
-      before_script:
-        - python -mpip install -U pip twine
-        - chmod a+rwx $HOME/.cache
-        - mkdir -p $HOME/.cache/pip
-        - chmod a+rwx $HOME/.cache/pip
+    # 32-bit manylinux temporarily commentted out.
+    # https://github.com/cython/cython/issues/3840 has surfaced again.
+    # - stage: test
+    #   name: 32-bit manylinux wheels (all Pythons)
+    #   language: python
+    #   services: docker
+    #   env: DOCKER_IMAGE=quay.io/pypa/manylinux2010_i686 PRE_CMD=linux32
+    #   install: docker pull $DOCKER_IMAGE
+    #   script: bash scripts/releases/make-manylinux
+    #   before_script:
+    #     - python -mpip install -U pip twine
+    #     - chmod a+rwx $HOME/.cache
+    #     - mkdir -p $HOME/.cache/pip
+    #     - chmod a+rwx $HOME/.cache/pip
 
     # Lint the code. Because this is a separate job, even if it fails fast
     # the tests will still run. Put it at the top for fast feedback.

docs/changes/issue1674.bugfix

 On CPython, depend on greenlet >= 0.4.17. This version is binary
-incompatible with earlier releases on CPython 3.7 and later. Note that
-gevent does not rely on its new support for context variables since
-gevent provides the same API to older versions of Python.
+incompatible with earlier releases on CPython 3.7 and later.
+
+On Python 3.7 and above, the module ``gevent.contextvars`` is no
+longer monkey-patched into the standard library. contextvars are now
+both greenlet and asyncio task local. See :issue:`1656`.

src/gevent/contextvars.py

@@ -3,7 +3,8 @@
 Cooperative ``contextvars`` module.
 
 This module was added to Python 3.7. The gevent version is available
-on all supported versions of Python.
+on all supported versions of Python. However, see an important note
+about gevent 20.9.
 
 Context variables are like greenlet-local variables, just more
 inconvenient to use. They were designed to work around limitations in
@@ -23,6 +24,17 @@ from :pep:`567` and doesn't have much optimization. In particular, setting
 context values isn't constant time.
 
 .. versionadded:: 1.5a3
+.. versionchanged:: NEXT
+   On Python 3.7 and above, this module is no longer monkey-patched
+   in place of the standard library version.
+   gevent depends on greenlet 0.4.17 which includes support for context variables.
+   This means that any number of greenlets can be running any number of asyncio tasks
+   each with their own context variables. This module is only greenlet aware, not
+   asyncio task aware, so its use is not recommended on Python 3.7 and above.
+
+   On previous versions of Python, this module continues to be a solution for
+   backporting code. It is also available if you wish to use the contextvar API
+   in a strictly greenlet-local manner.
 """
 from __future__ import absolute_import
 from __future__ import division

src/gevent/monkey.py

@@ -157,6 +157,7 @@ else:
 
 WIN = sys.platform.startswith("win")
 PY36 = sys.version_info[:2] >= (3, 6)
+PY37 = sys.version_info[:2] >= (3, 7)
 
 class _BadImplements(AttributeError):
     """
@@ -583,7 +584,16 @@ def patch_contextvars():
 
     .. versionchanged:: 20.04.0
        Clarify that the backport is also patched.
+
+    .. versionchanged:: NEXT
+       This now does nothing on Python 3.7 and above.
+       gevent now depends on greenlet 0.4.17, which
+       natively handles switching context vars when greenlets are switched.
+       Older versions of Python that have the backport installed will
+       still be patched.
     """
+    if PY37:
+        return
     try:
         __import__('contextvars')
     except ImportError: