matplotlib
diff --git a/‎lib/matplotlib/_layoutbox.py
Lines changed: 10 additions & 3 deletions b/‎lib/matplotlib/_layoutbox.py
Lines changed: 10 additions & 3 deletions
diff --git a/‎lib/matplotlib/animation.py
Lines changed: 12 additions & 32 deletions b/‎lib/matplotlib/animation.py
Lines changed: 12 additions & 32 deletions
@@ -44,6 +44,7 @@ def get_renderer(fig):
 
     return renderer
 
+len_seq = 6  # number of digints in unique id.  See seq_id below...
 
 class LayoutBox(object):
     """
@@ -354,7 +355,9 @@ def _is_subplotspec_layoutbox(self):
         Helper to check if this layoutbox is the layoutbox of a
         subplotspec
         '''
-        name = (self.name).split('.')[-1][:-3]
+        global len_seq
+
+        name = (self.name).split('.')[-1][:-len_seq]
         if name == 'ss':
             return True
         return False
@@ -364,7 +367,9 @@ def _is_gridspec_layoutbox(self):
         Helper to check if this layoutbox is the layoutbox of a
         gridspec
         '''
-        name = (self.name).split('.')[-1][:-3]
+        global len_seq
+
+        name = (self.name).split('.')[-1][:-len_seq]
         if name == 'gridspec':
             return True
         return False
@@ -645,8 +650,10 @@ def seq_id():
     '''
 
     global _layoutboxobjnum
+    global len_seq
 
-    return ('%03d' % (next(_layoutboxobjnum)))
+    fstr = '%0{}d'.format(len_seq)
+    return (fstr%(next(_layoutboxobjnum)))
 
 
 def print_children(lb):
 
@@ -25,6 +25,7 @@
 import os
 from pathlib import Path
 import platform
+import shutil
 import subprocess
 import sys
 from tempfile import TemporaryDirectory
@@ -408,27 +409,9 @@ def bin_path(cls):
     @classmethod
     def isAvailable(cls):
         '''
-        Check to see if a MovieWriter subclass is actually available by
-        running the commandline tool.
+        Check to see if a MovieWriter subclass is actually available.
         '''
-        bin_path = cls.bin_path()
-        if not bin_path:
-            return False
-        try:
-            p = subprocess.Popen(
-                bin_path,
-                shell=False,
-                stdout=subprocess.PIPE,
-                stderr=subprocess.PIPE,
-                creationflags=subprocess_creation_flags)
-            return cls._handle_subprocess(p)
-        except OSError:
-            return False
-
-    @classmethod
-    def _handle_subprocess(cls, process):
-        process.communicate()
-        return True
+        return shutil.which(cls.bin_path()) is not None
 
 
 class FileMovieWriter(MovieWriter):
@@ -633,13 +616,14 @@ def output_args(self):
         return args + ['-y', self.outfile]
 
     @classmethod
-    def _handle_subprocess(cls, process):
-        _, err = process.communicate()
-        # Ubuntu 12.04 ships a broken ffmpeg binary which we shouldn't use
-        # NOTE : when removed, remove the same method in AVConvBase.
-        if 'Libav' in err.decode():
-            return False
-        return True
+    def isAvailable(cls):
+        return (
+            super().isAvailable()
+            # Ubuntu 12.04 ships a broken ffmpeg binary which we shouldn't use.
+            # NOTE: when removed, remove the same method in AVConvBase.
+            and b'LibAv' not in subprocess.run(
+                [cls.bin_path()], creationflags=subprocess_creation_flags,
+                stdout=subprocess.DEVNULL, stderr=subprocess.PIPE).stderr)
 
 
 # Combine FFMpeg options with pipe-based writing
@@ -697,9 +681,7 @@ class AVConvBase(FFMpegBase):
     args_key = 'animation.avconv_args'
 
     # NOTE : should be removed when the same method is removed in FFMpegBase.
-    @classmethod
-    def _handle_subprocess(cls, process):
-        return MovieWriter._handle_subprocess(process)
+    isAvailable = classmethod(MovieWriter.isAvailable.__func__)
 
 
 # Combine AVConv options with pipe-based writing
@@ -772,8 +754,6 @@ def isAvailable(cls):
             cls._init_from_registry()
         return super().isAvailable()
 
-ImageMagickBase._init_from_registry()
-
 
 # Note: the base classes need to be in that order to get
 # isAvailable() from ImageMagickBase called and not the