Add Python 3.8 support (#31)

Author: briandealwis

python/Dockerfile

@@ -4,6 +4,9 @@ RUN PYTHONUSERBASE=/ptvsd pip install --user ptvsd
 FROM python:3.7 as python37
 RUN PYTHONUSERBASE=/ptvsd pip install --user ptvsd
 
+FROM python:3.8 as python38
+RUN PYTHONUSERBASE=/ptvsd pip install --user ptvsd
+
 # Now populate the duct-tape image with the language runtime debugging support files
 # The debian image is about 95MB bigger
 FROM busybox
@@ -13,3 +16,4 @@ CMD ["/bin/sh", "/install.sh"]
 WORKDIR /duct-tape
 COPY --from=python27 /ptvsd/ python/
 COPY --from=python37 /ptvsd/ python/
+COPY --from=python38 /ptvsd/ python/

test/structure-tests-python.yaml

@@ -5,6 +5,8 @@ fileExistenceTests:
     path: '/duct-tape/python/lib/python2.7/site-packages/ptvsd/__init__.py'
   - name: 'ptvsd for python 3.7'
     path: '/duct-tape/python/lib/python3.7/site-packages/ptvsd/__init__.py'
+  - name: 'ptvsd for python 3.8'
+    path: '/duct-tape/python/lib/python3.8/site-packages/ptvsd/__init__.py'
 
 commandTests:
   - name: "run with no /dbg should fail"