Force fail on Python 2. When doing so, emit an error that directs users to the...

Force fail on Python 2. When doing so, emit an error that directs users to the latest guidance. Fixes #2094.

.github/ISSUE_TEMPLATE/setuptools-warns-about-python-2-incompatibility.md

@@ -28,6 +28,7 @@ Your first course of action should be to reason about how you managed to get an
 <!-- These are the recommended workarounds for the issue. Please
 try them first. -->
 
+- [ ] Read [Python 2 Sunset docs](https://setuptools.readthedocs.io/en/latest/python%202%20sunset.html).
 - [ ] Python 2 is required for this application.
 - [ ] I maintain the software that installs Setuptools (if not, please contact that project).
 - [ ] Setuptools installed with pip 9 or later.

.travis.yml

@@ -4,11 +4,6 @@ language: python
 jobs:
   fast_finish: true
   include:
-  - &latest_py2
-    python: 2.7
-    env: TOXENV=py27
-  - <<: *latest_py2
-    env: LANG=C TOXENV=py27
   - python: pypy3
     env: DISABLE_COVERAGE=1  # Don't run coverage on pypy (too slow).
   - python: 3.5

pkg_resources/py2_warn.py

@@ -4,18 +4,13 @@ import textwrap
 
 
 msg = textwrap.dedent("""
-    You are running Setuptools on Python 2, which is no longer
-    supported and
-    >>> SETUPTOOLS WILL STOP WORKING <<<
-    in a subsequent release (no sooner than 2020-04-20).
-    Please ensure you are installing
-    Setuptools using pip 9.x or later or pin to `setuptools<45`
-    in your environment.
-    If you have done those things and are still encountering
-    this message, please follow up at
-    https://bit.ly/setuptools-py2-warning.
+    Encountered a version of Setuptools that no longer supports
+    this version of Python. Please head to
+    https://bit.ly/setuptools-py2-warning for support.
     """)
 
-pre = "Setuptools will stop working on Python 2\n"
+pre = "Setuptools no longer works on Python 2\n"
 
-sys.version_info < (3,) and warnings.warn(pre + "*" * 60 + msg + "*" * 60)
+if sys.version_info < (3,):
+    warnings.warn(pre + "*" * 60 + msg + "*" * 60)
+    raise SystemExit(32)