Install dev dependency when running apistub (Azure#12268)

Author: praveenkuttappan

eng/tox/tox.ini

@@ -224,7 +224,7 @@ skip_install = false
 usedevelop = true
 changedir = {toxinidir}
 deps =
-  astroid 
+  {[base]deps}
 commands =
     # install API stub generator
     {envbindir}/python -m pip install "git+https://github.com/Azure/azure-sdk-tools.git#subdirectory=packages/python-packages/api-stub-generator&egg=api-stub-generator"