remove last bits of python2 support (#80)

Remove string type compat check since py3.8 is the now the minimum.

jsondiff/__init__.py

@@ -1,4 +1,3 @@
-import sys
 import json
 import yaml
 
@@ -15,15 +14,6 @@
 # - when source is list and diff is a list patch dict -> patch
 # - else -> replacement
 
-# Python 2 vs 3
-PY3 = sys.version_info[0] == 3
-
-if PY3:
-    string_types = str
-else:
-    string_types = basestring
-
-
 class JsonDumper:
     def __init__(self, **kwargs):
         self.kwargs = kwargs
@@ -61,7 +51,7 @@ def __call__(self, src):
         :param src: str|file-like source
         :return: dict parsed data
         """
-        if isinstance(src, string_types):
+        if isinstance(src, str):
             return json.loads(src, **self.kwargs)
         else:
             return json.load(src, **self.kwargs)
@@ -1020,7 +1010,7 @@ def _unescape(self, x):
         """
         Unescapes a string that has been escaped.
         """
-        if isinstance(x, string_types):
+        if isinstance(x, str):
             sym = self._symbol_map.get(x, None)
             if sym is not None:
                 return sym
@@ -1051,7 +1041,7 @@ def _escape(self, o):
         """
         if type(o) is Symbol:
             return self.options.escape_str + o.label
-        if isinstance(o, string_types) and o.startswith(self.options.escape_str):
+        if isinstance(o, str) and o.startswith(self.options.escape_str):
             return self.options.escape_str + o
         return o