Migrate Python libraries to v3 (#2284)

* .gitignore migrations/0x_ganache_snapshot

* .gitignore new-ish Python contract wrappers

These should have been added back when we started generating these
wrappers.

* rm superfluous contract artifact in Python package

All of the contract artifacts were removed from the Python package
recently, because now they're copied from the monorepo/packages area as
an automated build step.  Somehow this one artifact slipped through the
cracks.

* Eliminate circular dependency

This was preventing the Exchange wrapper from ever importing its
validator!

* Improve output of monorepo-level parallel script

- Capture stderr (and have it included in stdout) so that it doesn't
leak onto the console for commands that didn't actually fail.

- Include all error output in the Exception object (eliminate print
statement).

* Silence new versions of linters

Newer versions care about this stuff.  Old versions didn't, and we don't
either.

* Support Rich Reverts via Web3.py middleware

* Fix bug in generated wrappers' bytes handling

`bytes.fromhex(bytes.decode('utf-8')` is just plain wrong.  It would
work for some cases, but is not working when trying to fill orders with
the latest Exchange contract.

* Migrate to Exchange v3

* Fix typo in DevUtils documentation

* Include new contracts in docs

* Re-enable Python checks in CI

* Accept strings for bytes

* Fix CircleCI build artifacts for gen'd python

I swear the previous way was working before, but it wasn't working now,
so this fixes it.

* Accept a provider OR a Web3 object

In various places.  This allows the caller to install middleware (which
in web3.py is installed on a Web3 object, not on a provider) before
executing any RPC calls, which is important for the case where one wants
to produce signatures locally before submitting to a remote node.

* wrapper base: don't assume there are accounts

* Eliminate some inline linter directives

* make CHANGELOGs be REVERSE chronological

* Update CHANGELOG entries and bump version numbers

* @0x/contract-addresses: Put addr's in JSON, not TS

This allows easier consumption by other languages.  (Specifically, it
eliminates the overhead of keeping the Python addresses package in sync
with the TypeScript one.)

* sra_client.py: incl. docker in `./setup.py clean`

* sra_client.py: Migrate to protocol v3

Removed script that existed only to exclude runs of sra_client builds
(parallel_without_sra_client).  Now `parallel` is used by CI,
re-including sra_client in CI checks.

* abi-gen/templates/Py: clarify if/else logic

In response to
https://github.com/0xProject/0x-monorepo/pull/2284#discussion_r342200906

* sra_client.py: Update CHANGELOG and bump version

* contract_addresses/setup.py: rm unnecessary rm

* json_schemas.py: corrections to dev dependencies

* In tests against deployment, also run doctests

* contract_wrappers example: rm xtra Order attribute

Thanks to @steveklebanoff for catching this.
https://github.com/0xProject/0x-monorepo/pull/2284#pullrequestreview-312065368

python-packages/contract_wrappers/setup.py

@@ -2,11 +2,15 @@
 
 """setuptools module for contract_wrappers package."""
 
+# pylint: disable=import-outside-toplevel
+# we import things outside of top-level because 3rd party libs may not yet be
+# installed when you invoke this script
+
 import subprocess  # nosec
 from shutil import rmtree
 from os import environ, path, remove
 from pathlib import Path
-from sys import argv
+from sys import argv, exit  # pylint: disable=redefined-builtin
 
 from distutils.command.clean import clean
 import distutils.command.build_py
@@ -192,7 +196,7 @@ with open("README.md", "r") as file_handle:
 
 setup(
     name="0x-contract-wrappers",
-    version="1.1.0",
+    version="2.0.0",
     description="Python wrappers for 0x smart contracts",
     long_description=README_MD,
     long_description_content_type="text/markdown",