[TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

modify smoketest.sh to python3.8

tests/pytest/smoketest.sh

@@ -2,36 +2,36 @@
 ulimit -c unlimited
 
 # insert
-python3 ./test.py $1 -f insert/basic.py
-python3 ./test.py $1 -s && sleep 1
-python3 ./test.py $1 -f insert/bigint.py
-python3 ./test.py $1 -s && sleep 1
-python3 ./test.py $1 -f insert/nchar.py
-python3 ./test.py $1 -s && sleep 1
-python3 ./test.py $1 -f insert/multi.py
-python3 ./test.py $1 -s && sleep 1
+python3.8 ./test.py $1 -f insert/basic.py
+python3.8 ./test.py $1 -s && sleep 1
+python3.8 ./test.py $1 -f insert/bigint.py
+python3.8 ./test.py $1 -s && sleep 1
+python3.8 ./test.py $1 -f insert/nchar.py
+python3.8 ./test.py $1 -s && sleep 1
+python3.8 ./test.py $1 -f insert/multi.py
+python3.8 ./test.py $1 -s && sleep 1
 
 # table
-python3 ./test.py $1 -f table/column_name.py
-python3 ./test.py $1 -s && sleep 1
-python3 ./test.py $1 -f table/column_num.py
-python3 ./test.py $1 -s && sleep 1
-python3 ./test.py $1 -f table/db_table.py
-python3 ./test.py $1 -s && sleep 1
+python3.8 ./test.py $1 -f table/column_name.py
+python3.8 ./test.py $1 -s && sleep 1
+python3.8 ./test.py $1 -f table/column_num.py
+python3.8 ./test.py $1 -s && sleep 1
+python3.8 ./test.py $1 -f table/db_table.py
+python3.8 ./test.py $1 -s && sleep 1
 
 # import
-python3 ./test.py $1 -f import_merge/importDataLastSub.py
-python3 ./test.py $1 -s && sleep 1
+python3.8 ./test.py $1 -f import_merge/importDataLastSub.py
+python3.8 ./test.py $1 -s && sleep 1
 
 #tag 
-python3 ./test.py $1 -f tag_lite/filter.py
-python3 ./test.py $1 -s && sleep 1
+python3.8 ./test.py $1 -f tag_lite/filter.py
+python3.8 ./test.py $1 -s && sleep 1
 
 #query
-python3 ./test.py $1 -f query/filter.py
-python3 ./test.py $1 -s && sleep 1
+python3.8 ./test.py $1 -f query/filter.py
+python3.8 ./test.py $1 -s && sleep 1
 
 # client
-python3 ./test.py $1 -f client/client.py
-python3 ./test.py $1 -s && sleep 1
+python3.8 ./test.py $1 -f client/client.py
+python3.8 ./test.py $1 -s && sleep 1