Replace pkg_resources.resource_string

Use an approach similar to the previous commit.

augur/validate.py

@@ -3,16 +3,15 @@
 """
 
 import sys
-import os
 from collections import defaultdict
 import json
 import jsonschema
 import jsonschema.exceptions
 import re
 from itertools import groupby
-from pkg_resources import resource_string
 from textwrap import indent
 from typing import Iterable, Union
+from augur.data import as_file
 from augur.io.print import print_err
 from augur.io.json import shorten_as_json
 from .validate_export import verifyMainJSONIsInternallyConsistent, verifyMetaAndOrTreeJSONsAreInternallyConsistent
@@ -31,7 +30,8 @@ def load_json_schema(path):
     (located in augur/data)
     '''
     try:
-        schema = json.loads(resource_string(__package__, os.path.join("data", path)))
+        with as_file(path) as file, open(file, "r", encoding = "utf-8") as fh:
+            schema = json.load(fh)
     except json.JSONDecodeError as err:
         raise ValidateError("Schema {} is not a valid JSON file. Error: {}".format(path, err))
     # check loaded schema is itself valid -- see http://python-jsonschema.readthedocs.io/en/latest/errors/