Fix python 3.9 compatibility

Fixes #233

Author: qu1ck

InteractiveHtmlBom/ecad/__init__.py

@@ -10,7 +10,7 @@ def get_parser_by_extension(file_name, config, logger):
         import io
         import json
         with io.open(file_name, 'r', encoding='utf-8') as f:
-            obj = json.load(f, encoding='utf-8')
+            obj = json.load(f)
         if 'pcbdata' in obj:
             return get_generic_json_parser(file_name, config, logger)
         else:

InteractiveHtmlBom/ecad/easyeda.py

@@ -25,7 +25,7 @@ class EasyEdaParser(EcadParser):
     def get_easyeda_pcb(self):
         import json
         with io.open(self.file_name, 'r', encoding='utf-8') as f:
-            return json.load(f, encoding='utf-8')
+            return json.load(f)
 
     @staticmethod
     def tilda_split(s):

InteractiveHtmlBom/ecad/genericjson.py

@@ -11,7 +11,7 @@ class GenericJsonParser(EcadParser):
     def get_generic_json_pcb(self):
         from os import path
         with io.open(self.file_name, 'r', encoding='utf-8') as f:
-            pcb = json.load(f, encoding='utf-8')
+            pcb = json.load(f)
 
         if 'spec_version' not in pcb:
             raise ValidationError("'spec_version' is a required property")
@@ -26,7 +26,7 @@ def get_generic_json_pcb(self):
                                      .format(pcb['spec_version']))
 
         with io.open(schema_file_name, 'r', encoding='utf-8') as f:
-            schema = json.load(f, encoding='utf-8')
+            schema = json.load(f)
 
         validate(instance=pcb, schema=schema)