Get ready for release 9.0.1

Author: rocky

admin-tools/check-versions.sh

@@ -19,6 +19,7 @@ for version in $PYVERSIONS; do
 	exit $?
     fi
     make clean && pip install -e .
+    make develop
     if ! make check; then
 	exit $?
     fi

pymathics/natlang/version.py

@@ -5,4 +5,4 @@
 # well as importing into Python. That's why there is no
 # space around "=" below.
 # fmt: off
-__version__="9.0.0"  # noqa
+__version__="9.0.1"  # noqa