MNT: Remove ability to pass URLs to imread()

This follows the deprecation period.

Author: greglucas

doc/api/next_api_changes/removals/23XXX-GL.rst

@@ -26,3 +26,11 @@ Parameters of the Axes constructor other than *fig* and *rect* are now keyword o
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Use ``docutils.parsers.rst.directives.images.Image.align`` instead.
+
+``imread()`` no longer accepts URLs
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Passing a URL to `~.pyplot.imread()` has been removed. Please open the URL for
+reading and directly use the Pillow API
+(``PIL.Image.open(urllib.request.urlopen(url))``, or
+``PIL.Image.open(io.BytesIO(requests.get(url).content))``) instead.

lib/matplotlib/image.py

@@ -1526,29 +1526,13 @@ def imread(fname, format=None):
         ext = format
     img_open = (
         PIL.PngImagePlugin.PngImageFile if ext == 'png' else PIL.Image.open)
-    if isinstance(fname, str):
-        parsed = parse.urlparse(fname)
-        if len(parsed.scheme) > 1:  # Pillow doesn't handle URLs directly.
-            _api.warn_deprecated(
-                "3.4", message="Directly reading images from URLs is "
-                "deprecated since %(since)s and will no longer be supported "
-                "%(removal)s. Please open the URL for reading and pass the "
-                "result to Pillow, e.g. with "
-                "``np.array(PIL.Image.open(urllib.request.urlopen(url)))``.")
-            # hide imports to speed initial import on systems with slow linkers
-            from urllib import request
-            ssl_ctx = mpl._get_ssl_context()
-            if ssl_ctx is None:
-                _log.debug(
-                    "Could not get certifi ssl context, https may not work."
-                )
-            with request.urlopen(fname, context=ssl_ctx) as response:
-                import io
-                try:
-                    response.seek(0)
-                except (AttributeError, io.UnsupportedOperation):
-                    response = io.BytesIO(response.read())
-                return imread(response, format=ext)
+    if isinstance(fname, str) and len(parse.urlparse(fname).scheme) > 1:
+        # Pillow doesn't handle URLs directly.
+        raise ValueError(
+            "Please open the URL for reading and pass the "
+            "result to Pillow, e.g. with "
+            "``np.array(PIL.Image.open(urllib.request.urlopen(url)))``."
+            )
     with img_open(fname) as image:
         return (_pil_png_to_float_array(image)
                 if isinstance(image, PIL.PngImagePlugin.PngImageFile) else

lib/matplotlib/tests/test_image.py

@@ -13,7 +13,7 @@
 
 import matplotlib as mpl
 from matplotlib import (
-    _api, colors, image as mimage, patches, pyplot as plt, style, rcParams)
+    colors, image as mimage, patches, pyplot as plt, style, rcParams)
 from matplotlib.image import (AxesImage, BboxImage, FigureImage,
                               NonUniformImage, PcolorImage)
 from matplotlib.testing.decorators import check_figures_equal, image_comparison
@@ -720,7 +720,7 @@ def test_load_from_url():
     url = ('file:'
            + ('///' if sys.platform == 'win32' else '')
            + path.resolve().as_posix())
-    with _api.suppress_matplotlib_deprecation_warning():
+    with pytest.raises(ValueError, match="Please open the URL"):
         plt.imread(url)
     with urllib.request.urlopen(url) as file:
         plt.imread(file)
@@ -1139,13 +1139,6 @@ def test_exact_vmin():
     assert np.all(from_image == direct_computation)
 
 
-@pytest.mark.network
-@pytest.mark.flaky
-def test_https_imread_smoketest():
-    with _api.suppress_matplotlib_deprecation_warning():
-        v = mimage.imread('https://matplotlib.org/1.5.0/_static/logo2.png')
-
-
 # A basic ndarray subclass that implements a quantity
 # It does not implement an entire unit system or all quantity math.
 # There is just enough implemented to test handling of ndarray