Require Python 3 for installation.

QuLogic · tacaswell · commit c36902c19622 · 2018-02-13T08:57:20.000-05:00
This change is based on the work that IPython did for their transition to Python 3-only [1]. [1] https://www.youtube.com/watch?v=2DkfPzWWC2Q
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -99,6 +99,8 @@
 to MATLAB&reg;, a registered trademark of The MathWorks, Inc.
 
 """
+# NOTE: This file must remain Python 2 compatible for the forseeable future,
+# to ensure that we error out properly for existing editable installs.
 from __future__ import absolute_import, division, print_function
 
 import six
@@ -122,6 +124,17 @@
 import tempfile
 import warnings
 
+if sys.version_info < (3, 5):  # noqa: E402
+    raise ImportError("""
+Matplotlib 3.0+ does not support Python 2.x, 3.0, 3.1, 3.2, 3.3, or 3.4.
+Beginning with Matplotlib 3.0, Python 3.5 and above is required.
+
+See Matplotlib `INSTALL.rst` file for more information:
+
+    https://github.com/matplotlib/matplotlib/blob/master/INSTALL.rst
+
+""")
+
 # cbook must import matplotlib only within function
 # definitions, so it is safe to import from it here.
 from . import cbook
diff --git a/setup.py b/setup.py
@@ -3,6 +3,9 @@
 setup.cfg.template for more information.
 """
 
+# NOTE: This file must remain Python 2 compatible for the forseeable future,
+# to ensure that we error out properly for people with outdated setuptools
+# and/or pip.
 from __future__ import print_function, absolute_import
 from string import Template
 from setuptools import setup
@@ -265,6 +268,7 @@ def run(self):
         classifiers=classifiers,
         download_url="http://matplotlib.org/users/installing.html",
 
+        python_requires='>=3.5',
         # List third-party Python packages that we require
         install_requires=install_requires,
         setup_requires=setup_requires,
diff --git a/setupext.py b/setupext.py
@@ -1,3 +1,6 @@
+# NOTE: This file must remain Python 2 compatible for the forseeable future,
+# to ensure that we error out properly for people with outdated setuptools
+# and/or pip.
 from __future__ import print_function, absolute_import
 
 from importlib import import_module
@@ -680,15 +683,16 @@ class Python(SetupPackage):
     def check(self):
         major, minor1, minor2, s, tmp = sys.version_info
 
-        if major < 2:
-            raise CheckFailed(
-                "Requires Python 2.7 or later")
-        elif major == 2 and minor1 < 7:
-            raise CheckFailed(
-                "Requires Python 2.7 or later (in the 2.x series)")
-        elif major == 3 and minor1 < 4:
-            raise CheckFailed(
-                "Requires Python 3.4 or later (in the 3.x series)")
+        if major < 3 or minor1 < 5:
+            error = """
+Matplotlib 3.0+ does not support Python 2.x, 3.0, 3.1, 3.2, 3.3, or 3.4.
+Beginning with Matplotlib 3.0, Python 3.5 and above is required.
+
+This may be due to an out of date pip.
+
+Make sure you have pip >= 9.0.1.
+"""
+            raise CheckFailed(error)
 
         return sys.version
 
