feat(order_utils.py): sign_hash() (#1254)

Also moved is_valid_signature() into main package module, for
simplicity.

Also consolidated a handul of in-line pylint disable directives into the
.pylintrc config file.

python-packages/order_utils/test/test_doctest.py

@@ -8,7 +8,6 @@ import zero_ex
 
 def test_all_doctests():
     """Gather zero_ex.* modules and doctest them."""
-    # prefer `black` formatting. pylint: disable=bad-continuation
     for (importer, modname, _) in pkgutil.walk_packages(
         path=zero_ex.__path__, prefix="zero_ex."
     ):

python-packages/order_utils/test/test_generate_order_hash_hex.py

@@ -3,7 +3,7 @@
 from zero_ex.order_utils import (
     generate_order_hash_hex,
     make_empty_order,
-    Constants,
+    _Constants,
 )
 
 
@@ -13,6 +13,6 @@ def test_get_order_hash_hex__empty_order():
         "faa49b35faeb9197e9c3ba7a52075e6dad19739549f153b77dfcf59408a4b422"
     )
     actual_hash_hex = generate_order_hash_hex(
-        make_empty_order(), Constants.null_address
+        make_empty_order(), _Constants.null_address
     )
     assert actual_hash_hex == expected_hash_hex

python-packages/order_utils/test/test_signature_utils.py

@@ -3,7 +3,7 @@
 import pytest
 from web3 import Web3
 
-from zero_ex.order_utils.signature_utils import is_valid_signature
+from zero_ex.order_utils import is_valid_signature
 
 
 def test_is_valid_signature__provider_wrong_type():