DEP: Remove _convert_asset_str_fields

_convert_asset_str_fields was added to address the fact that the
unicode returned by SQLAlchemy was causing test failures, in
particular test_repr and test_root_symbols failed because of the
leading 'u' character in the unicode of python-2.x. Later it was
pointed out that this method would behave differently in python 2
and 3, in particular the str() method would return bytes in python
2 and unicode in python 3. After investigating it was found that
the _convert_asset_str_fields was no longer  necessary. It is unclear
why the original tests were failing. It is not due to SQLAlchemy
versions, as tests pass for version >1 and <1.

zipline/assets/assets.py

@@ -63,16 +63,6 @@ _asset_timestamp_fields = frozenset({
 })
 
 
-def _convert_asset_str_fields(dict):
-    """
-    Takes in a dict of Asset init args and converts from unicode to string
-    where applicable
-    """
-    for key, value in dict.items():
-        if key in _asset_str_fields:
-            dict[key] = str(value)
-
-
 def _convert_asset_timestamp_fields(dict):
     """
     Takes in a dict of Asset init args and converts dates to pd.Timestamps
@@ -228,7 +218,6 @@ class AssetFinder(object):
         # Convert 'data' from a RowProxy object to a dict, to allow assignment
         data = dict(data.items())
         if data:
-            _convert_asset_str_fields(data)
             _convert_asset_timestamp_fields(data)
 
             equity = Equity(**data)
@@ -251,7 +240,6 @@ class AssetFinder(object):
         # Convert 'data' from a RowProxy object to a dict, to allow assignment
         data = dict(data.items())
         if data:
-            _convert_asset_str_fields(data)
             _convert_asset_timestamp_fields(data)
 
             future = Future(**data)