using jsonlines to read manifest and dump decode result

deepspeech/frontend/utility.py

@@ -12,7 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 """Contains data helper functions."""
-import codecs
 import json
 import math
 from typing import List
@@ -92,12 +91,8 @@ def read_manifest(
     """
 
     manifest = []
-    for json_line in codecs.open(manifest_path, 'r', 'utf-8'):
-        try:
-            json_data = json.loads(json_line)
-        except Exception as e:
-            raise IOError("Error reading manifest: %s" % str(e))
-
+    with jsonlines.open(manifest_path, 'r') as reader:
+        for json_data in reader:
             feat_len = json_data["feat_shape"][
                 0] if 'feat_shape' in json_data else 1.0
             token_len = json_data["token_shape"][