Py2 fix for DataFrameCache - see apache#3302

contrib/connectors/pandas/cache.py

@@ -56,7 +56,7 @@ def _prune(self):
             for idx, cname in enumerate(entries):
                 mname = os.path.splitext(cname)[0] + self._fs_metadata_suffix
                 try:
-                    with open(mname, 'r', encoding='utf-8') as f:
+                    with open(mname, 'r') as f:
                         metadata = json.load(f)
                 except (IOError, OSError):
                     metadata = {'expires': -1}
@@ -84,7 +84,7 @@ def get(self, key):
         cname = filename + self._fs_cache_suffix
         mname = filename + self._fs_metadata_suffix
         try:
-            with open(mname, 'r', encoding='utf-8') as f:
+            with open(mname, 'r') as f:
                 metadata = json.load(f)
         except (IOError, OSError):
             metadata = {'expires': -1}
@@ -134,7 +134,7 @@ def set(self, key, value, timeout=None):
                         metadata['format'] = 'pickle'
             rename(tmp, cname)
             os.chmod(cname, self._mode)
-            with open(mname, 'w', encoding='utf-8') as f:
+            with open(mname, 'w') as f:
                 json.dump(metadata, f)
             os.chmod(mname, self._mode)
         except (IOError, OSError):
@@ -159,7 +159,7 @@ def has(self, key):
         cname = filename + self._fs_cache_suffix
         mname = filename + self._fs_metadata_suffix
         try:
-            with open(mname, 'r', encoding='utf-8') as f:
+            with open(mname, 'r') as f:
                 metadata = json.load(f)
         except (IOError, OSError):
             metadata = {'expires': -1}