Remove deprecated code due for removal in Pillow 4.2 (per PR #2010)

PIL/JpegImagePlugin.py

@@ -554,7 +554,6 @@ RAWMODE = {
     "1": "L",
     "L": "L",
     "RGB": "RGB",
-    "RGBA": "RGB",
     "RGBX": "RGB",
     "CMYK": "CMYK;I",  # assume adobe conventions
     "YCbCr": "YCbCr",
@@ -603,14 +602,6 @@ def _save(im, fp, filename):
     except KeyError:
         raise IOError("cannot write mode %s as JPEG" % im.mode)
 
-    if im.mode == 'RGBA':
-        warnings.warn(
-            'You are saving RGBA image as JPEG. The alpha channel will be '
-            'discarded. This conversion is deprecated and will be disabled '
-            'in Pillow 3.7. Please, convert the image to RGB explicitly.',
-            DeprecationWarning
-        )
-
     info = im.encoderinfo
 
     dpi = [int(round(x)) for x in info.get("dpi", (0, 0))]

Tests/test_file_jpeg.py

@@ -476,17 +476,11 @@ class TestFileJpeg(PillowTestCase):
             img.save(out, "JPEG")
 
     def test_save_wrong_modes(self):
-        out = BytesIO()
-        for mode in ['LA', 'La', 'RGBa', 'P']:
-            img = Image.new(mode, (20, 20))
-            self.assertRaises(IOError, img.save, out, "JPEG")
-
-    def test_save_modes_with_warnings(self):
         # ref https://github.com/python-pillow/Pillow/issues/2005
         out = BytesIO()
-        for mode in ['RGBA']:
+        for mode in ['LA', 'La', 'RGBA', 'RGBa', 'P']:
             img = Image.new(mode, (20, 20))
-            self.assert_warning(DeprecationWarning, img.save, out, "JPEG")
+            self.assertRaises(IOError, img.save, out, "JPEG")
 
     def test_save_tiff_with_dpi(self):
         # Arrange

docs/releasenotes/4.2.0.rst

@@ -7,3 +7,5 @@ Removed Deprecated Items
 Several deprecated items have been removed.
 
 * The methods :py:meth:`PIL.ImageWin.Dib.fromstring` and :py:meth:`PIL.ImageWin.Dib.tostring` have been removed.
+
+* Before Pillow 4.2.0, attempting to save an RGBA image as JPEG would discard the alpha channel. From Pillow 3.4.0, a deprecation warning was shown. From Pillow 4.2.0, the deprecation warning is removed and an :py:exc:`IOError` is raised.