catch OSError instead of FileNotFoundError to resolve matplotlib#15399

While finding available movie writers, if the executable is presented but
cannot be run, the import process will fail upon calling '_get_executable_info'
since it only handled CalledProcessError and FileNotFoundError.

In this commit, we catch OSError instead of FileNotFoundError in '__init__.py'
and log the error message in 'animation.py' to improve the import robustness.

Author: immaxchen

lib/matplotlib/__init__.py

@@ -337,8 +337,8 @@ def impl(args, regex, min_ver=None, ignore_exit_code=False):
                 output = _cpe.output
             else:
                 raise ExecutableNotFoundError(str(_cpe)) from _cpe
-        except FileNotFoundError as _fnf:
-            raise ExecutableNotFoundError(str(_fnf)) from _fnf
+        except OSError as _ose:
+            raise ExecutableNotFoundError(str(_ose)) from _ose
         match = re.search(regex, output)
         if match:
             version = LooseVersion(match.group(1))

lib/matplotlib/animation.py

@@ -723,8 +723,9 @@ def bin_path(cls):
     def isAvailable(cls):
         try:
             return super().isAvailable()
-        except mpl.ExecutableNotFoundError:
+        except mpl.ExecutableNotFoundError as _enf:
             # May be raised by get_executable_info.
+            _log.debug('ImageMagick unavailable due to: %s', _enf)
             return False