freeze CI requirements (google#431)

* freeze CI requirements, including pylint

.github/scripts/build.sh

@@ -19,11 +19,7 @@ set -e
 
 PYTHON_VERSION=${PYTHON_VERSION:-2.7}
 
-pip install --upgrade setuptools pip
-pip install --upgrade pylint pytest pytest-pylint pytest-runner
-pip install termcolor
-pip install hypothesis python-Levenshtein
-pip install mock
+pip install -U -r requirements.txt
 python setup.py develop
 python -m pytest  # Run the tests without IPython.
 pip install ipython

.github/scripts/requirements.txt

@@ -0,0 +1,10 @@
+setuptools <65.7.0
+pip <23.0
+pylint <2.15.10
+pytest <=7.2.1
+pytest-pylint <=1.1.2
+pytest-runner <6.0.0
+termcolor <2.2.0
+hypothesis <6.62.0
+python-Levenshtein <0.20.9
+mock <5.0.0