Merge pull request matplotlib#17883 from QuLogic/remove-py36

Remove Python 3.6 compatibility shims

lib/matplotlib/backends/backend_agg.py

@@ -25,10 +25,7 @@
     import threading
 except ImportError:
     import dummy_threading as threading
-try:
-    from contextlib import nullcontext
-except ImportError:
-    from contextlib import ExitStack as nullcontext  # Py 3.6.
+from contextlib import nullcontext
 from math import radians, cos, sin
 
 import numpy as np

lib/matplotlib/backends/backend_gtk3cairo.py

@@ -1,7 +1,4 @@
-try:
-    from contextlib import nullcontext
-except ImportError:
-    from contextlib import ExitStack as nullcontext  # Py 3.6.
+from contextlib import nullcontext
 
 from . import backend_cairo, backend_gtk3
 from .backend_gtk3 import Gtk, _BackendGTK3

lib/matplotlib/testing/decorators.py

@@ -9,10 +9,6 @@
 import sys
 import unittest
 import warnings
-try:
-    from contextlib import nullcontext
-except ImportError:
-    from contextlib import ExitStack as nullcontext  # Py3.6.
 
 import matplotlib as mpl
 import matplotlib.style
@@ -219,7 +215,8 @@ def compare(self, idx, baseline, extension, *, _lock=False):
                               {'Creator': None, 'Producer': None,
                                'CreationDate': None})
 
-        lock = cbook._lock_path(actual_path) if _lock else nullcontext()
+        lock = (cbook._lock_path(actual_path)
+                if _lock else contextlib.nullcontext())
         with lock:
             fig.savefig(actual_path, **kwargs)
             expected_path = self.copy_baseline(baseline, extension)

lib/matplotlib/tests/test_figure.py

@@ -1,13 +1,10 @@
+from contextlib import nullcontext
 from datetime import datetime
 import io
 from pathlib import Path
 import platform
 from types import SimpleNamespace
 import warnings
-try:
-    from contextlib import nullcontext
-except ImportError:
-    from contextlib import ExitStack as nullcontext  # Py3.6
 
 import matplotlib as mpl
 from matplotlib import cbook, rcParams

lib/matplotlib/tests/test_ticker.py

@@ -1,7 +1,4 @@
-try:
-    from contextlib import nullcontext
-except ImportError:
-    from contextlib import ExitStack as nullcontext  # Py 3.6.
+from contextlib import nullcontext
 import re
 import itertools
 

setup.py

@@ -258,9 +258,9 @@ def build_extensions(self):
         'License :: OSI Approved :: Python Software Foundation License',
         'Programming Language :: Python',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
+        'Programming Language :: Python :: 3.9',
         'Topic :: Scientific/Engineering :: Visualization',
     ],