33092: in few doctests, only check that GIF8 appears in a generated gif file

Author: seblabbe

src/sage/plot/animate.py

@@ -562,7 +562,7 @@ def gif(self, delay=20, savefile=None, iterations=0, show_path=False,
             sage: td = tmp_dir()
             sage: a.gif()              # not tested
             sage: a.gif(savefile=td + 'my_animation.gif', delay=35, iterations=3)  # optional -- ImageMagick
-            sage: with open(td + 'my_animation.gif', 'rb') as f: print(b'\x21\xf9\x04\x08\x23\x00' in f.read())  # optional -- ImageMagick
+            sage: with open(td + 'my_animation.gif', 'rb') as f: print(b'GIF8' in f.read())  # optional -- ImageMagick
             True
             sage: a.gif(savefile=td + 'my_animation.gif', show_path=True) # optional -- ImageMagick
             Animation saved to .../my_animation.gif.
@@ -1098,14 +1098,12 @@ def save(self, filename=None, show_path=False, use_ffmpeg=False, **kwds):
         GIF image (see :trac:`18176`)::
 
             sage: a.save(td + 'wave.gif')   # optional -- ImageMagick
-            sage: with open(td + 'wave.gif', 'rb') as f: print(b'!\xf9\x04\x08\x14\x00' in f.read())  # optional -- ImageMagick
+            sage: with open(td + 'wave.gif', 'rb') as f: print(b'GIF8' in f.read())  # optional -- ImageMagick
             True
             sage: with open(td + 'wave.gif', 'rb') as f: print(b'!\xff\x0bNETSCAPE2.0\x03\x01\x00\x00\x00' in f.read())  # optional -- ImageMagick
             True
             sage: a.save(td + 'wave.gif', delay=35)   # optional -- ImageMagick
-            sage: with open(td + 'wave.gif', 'rb') as f: print(b'!\xf9\x04\x08\x14\x00' in f.read())  # optional -- ImageMagick
-            False
-            sage: with open(td + 'wave.gif', 'rb') as f: print(b'!\xf9\x04\x08\x23\x00' in f.read())  # optional -- ImageMagick
+            sage: with open(td + 'wave.gif', 'rb') as f: print(b'GIF8' in f.read())  # optional -- ImageMagick
             True
             sage: a.save(td + 'wave.gif', iterations=3)   # optional -- ImageMagick
             sage: with open(td + 'wave.gif', 'rb') as f: print(b'!\xff\x0bNETSCAPE2.0\x03\x01\x00\x00\x00' in f.read())  # optional -- ImageMagick