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/src/zero_ex/dev_utils/abi_utils.py

@@ -84,7 +84,6 @@ def method_id(name: str, types: List[str]) -> str:
 
 
 def simple_encode(method: str, *args: Any) -> bytes:
-    # docstring considered all one line by pylint: disable=line-too-long
     r"""Encode a method ABI.
 
     >>> simple_encode("ERC20Token(address)", "0x1dc4c1cefef38a777b15aa20260a54e584b16c48")

python-packages/order_utils/src/zero_ex/dev_utils/type_assertions.py

@@ -2,6 +2,9 @@
 
 from typing import Any
 
+from eth_utils import is_address
+from web3.providers.base import BaseProvider
+
 
 def assert_is_string(value: Any, name: str) -> None:
     """If :param value: isn't of type str, raise a TypeError.
@@ -56,3 +59,31 @@ def assert_is_hex_string(value: Any, name: str) -> None:
     """
     assert_is_string(value, name)
     int(value, 16)  # raises a ValueError if value isn't a base-16 str
+
+
+def assert_is_address(value: Any, name: str) -> None:
+    """Assert that `value` is a valid Ethereum address.
+
+    If `value` isn't a hex string, raise a TypeError.  If it isn't a valid
+    Ethereum address, raise a ValueError.
+    """
+    assert_is_hex_string(value, name)
+    if not is_address(value):
+        raise ValueError(
+            f"Expected variable '{name}' to be a valid Ethereum"
+            + " address, but it's not."
+        )
+
+
+def assert_is_provider(value: Any, name: str) -> None:
+    """Assert that `value` is a Web3 provider.
+
+    If `value` isn't a Web3 provider, raise a TypeError.
+    """
+    # TODO: make this provider check more flexible.
+    # https://app.asana.com/0/684263176955174/901300863045491/f
+    if not isinstance(value, BaseProvider):
+        raise TypeError(
+            f"Expected variable '{name}' to be an instance of a Web3 provider,"
+            + " but it's not."
+        )