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/sra_client/test/relayer/docker-compose.yml

@@ -1,14 +1,36 @@
-# Run Launch Kit with Ganache as the backing node
+# Run Launch Kit Backend with Ganache and Mesh instances backing it.
 version: '3'
 services:
     ganache:
-        image: "0xorg/ganache-cli:2.2.2"
+        image: "0xorg/ganache-cli:4.4.0-beta.1"
         ports:
             - "8545:8545"
-    launchkit:
-        image: "0xorg/launch-kit-backend:74bcc39"
+        environment:
+            - VERSION=4.4.0-beta.1
+            - SNAPSHOT_NAME=0x_ganache_snapshot-v3-beta
+    mesh:
+        image: 0xorg/mesh:6.0.0-beta-0xv3
         depends_on:
             - ganache
+        environment:
+            ETHEREUM_RPC_URL: 'http://localhost:8545'
+            ETHEREUM_NETWORK_ID: '50'
+            ETHEREUM_CHAIN_ID: '1337'
+            USE_BOOTSTRAP_LIST: 'true'
+            VERBOSITY: 3
+            PRIVATE_KEY_PATH: ''
+            BLOCK_POLLING_INTERVAL: '5s'
+            P2P_LISTEN_PORT: '60557'
+        ports:
+            - '60557:60557'
+        network_mode: "host" # to connect to ganache
+        command: |
+            sh -c "waitForGanache () { until printf 'POST /\r\nContent-Length: 26\r\n\r\n{\"method\":\"net_listening\"}' | nc localhost 8545 | grep true; do continue; done }; waitForGanache && ./mesh"
+    launch-kit-backend:
+        image: "0xorg/launch-kit-backend:v3"
+        depends_on:
+            - ganache
+            - mesh
         ports:
             - "3000:3000"
         network_mode: "host" # to connect to ganache
@@ -16,5 +38,9 @@ services:
             - NETWORK_ID=50
             - RPC_URL=http://localhost:8545
             - WHITELIST_ALL_TOKENS=True
+            - FEE_RECIPIENT=0x0000000000000000000000000000000000000001
+            - MAKER_FEE_UNIT_AMOUNT=0
+            - TAKER_FEE_UNIT_AMOUNT=0
+            - MESH_ENDPOINT=ws://localhost:60557
         command: |
-            sh -c "until printf 'POST /\r\nContent-Length: 26\r\n\r\n{\"method\":\"net_listening\"}' | nc localhost 8545 | grep true; do continue; done; node_modules/.bin/forever ts/lib/index.js"
+            sh -c "waitForMesh () { sleep 3; }; waitForMesh && sleep 5 && node_modules/.bin/forever ts/lib/index.js"