Replace past.builtins.basestring with a custom one to workaround bug in Ubuntu's Python3

ffmpeg/_ffmpeg.py

@@ -1,6 +1,6 @@
 from __future__ import unicode_literals
 
-from past.builtins import basestring
+from ._utils import basestring
 
 from .nodes import (
     filter_operator,

ffmpeg/_run.py

@@ -2,7 +2,7 @@ from __future__ import unicode_literals
 
 from .dag import get_outgoing_edges, topo_sort
 from functools import reduce
-from past.builtins import basestring
+from ._utils import basestring
 import copy
 import operator
 import subprocess as _subprocess

ffmpeg/_utils.py

@@ -1,8 +1,42 @@
 from __future__ import unicode_literals
-
-from builtins import str
-from past.builtins import basestring
 import hashlib
+import sys
+
+if sys.version_info.major == 2:
+    # noinspection PyUnresolvedReferences,PyShadowingBuiltins
+    str = unicode
+
+
+# `past.builtins.basestring` module can't be imported on Python3 in some environments (Ubuntu).
+# This code is copy-pasted from it to avoid crashes.
+class BaseBaseString(type):
+    def __instancecheck__(cls, instance):
+        return isinstance(instance, (bytes, str))
+
+    def __subclasshook__(cls, thing):
+        # TODO: What should go here?
+        raise NotImplemented
+
+
+def with_metaclass(meta, *bases):
+    class metaclass(meta):
+        __call__ = type.__call__
+        __init__ = type.__init__
+
+        def __new__(cls, name, this_bases, d):
+            if this_bases is None:
+                return type.__new__(cls, name, (), d)
+            return meta(name, bases, d)
+
+    return metaclass('temporary_class', None, {})
+
+
+if sys.version_info.major >= 3:
+    class basestring(with_metaclass(BaseBaseString)):
+        pass
+else:
+    # noinspection PyUnresolvedReferences,PyCompatibility
+    from builtins import basestring
 
 
 def _recursive_repr(item):
@@ -27,6 +61,7 @@ def get_hash(item):
     repr_ = _recursive_repr(item).encode('utf-8')
     return hashlib.md5(repr_).hexdigest()
 
+
 def get_hash_int(item):
     return int(get_hash(item), base=16)