Support 6.2.x and 6.3.x in devcontainer

6.3 changed the bindingtester code to use Python3, so we need to make
sure to install the Python bindings (used by the binding tester) with
the right version of Python conditional on the minor version of FDB.

.devcontainer/Dockerfile

@@ -20,12 +20,15 @@ RUN set -ex; \
 
 # FDB bindings tester uses the Python bindings; install them from a
 # package to avoid building FDB from source
-# TODO FDB 6.3+ uses python3, we'll need to update it here
 RUN set -ex; \
     wget https://www.foundationdb.org/downloads/${FDB_VERSION}/bindings/python/foundationdb-${FDB_VERSION}.tar.gz; \
     tar zxf foundationdb-${FDB_VERSION}.tar.gz; \
     cd foundationdb-${FDB_VERSION}; \
-    python setup.py install; \
+    if [ "${FDB_VERSION}" < "6.3.0" ]; then \
+        python setup.py install; \
+    else \
+        python3 setup.py install; \
+    fi; \
     rm ../foundationdb-${FDB_VERSION}.tar.gz
 
 # Clone FoundationDB repo to retrieve bindings tester package and