Add support for python 3.9

Author: palango

.github/workflows/python-package.yml

@@ -12,7 +12,7 @@ jobs:
 
     strategy:
       matrix:
-        python-version: [3.7, 3.8]
+        python-version: [3.7, 3.8, 3.9]
 
     steps:
     - uses: actions/checkout@v2
@@ -52,7 +52,7 @@ jobs:
     - name: Test
       run: |
         source ./venv/bin/activate
-        pytest --cov=./ raiden_contracts/tests/ -v -n 4 --cov-config setup.cfg
+        pytest --cov=./ raiden_contracts/tests/ -v -n 2 --cov-config setup.cfg
     - name: Codecov
       run: |
         source ./venv/bin/activate

README.rst

@@ -12,7 +12,7 @@ Raiden Network Smart Contracts
 Prerequisites
 -------------
 
--  Python 3.7 or 3.8
+-  Python 3.7, 3.8 or 3.9
 -  https://pip.pypa.io/en/stable/
 
 Installation

setup.py

@@ -99,6 +99,7 @@ def run(self) -> None:  # pylint: disable=no-self-use
         "Programming Language :: Python :: 3",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
     ],
     "entry_points": {"console_scripts": ["deploy = raiden_contracts.deploy.__main__:main"]},
     "cmdclass": {