[tools] couchbase-cli broken when upgrade from 6.0.1 to 6.6.0 in Ubuntu 18.04

Steps to Reproduce

1. Install Couchbase server 6.0.1 on a Ubuntu 18.04 server.
2. Use couchbase-cli to initial node and create bucket1.  It works as expected.
3. Upgrade node to Couchbase server 6.6.0
   #Use couchbase-cli to create a second bucket, bucket2, failed with error: 

   root@ip-172-31-18-93:~# /opt/couchbase/bin/couchbase-cli bucket-create -c localhost:8091 --username Administrator --password password --bucket bucket2 --bucket-type couchbase --bucket-ramsize 256 --bucket-replica 1 --bucket-priority high --bucket-eviction-policy fullEviction --enable-flush 0 --enable-index-replica 1

   Traceback (most recent call last):

   File "/opt/couchbase/lib/python/couchbase-cli", line 8, in <module>

   import cbmgr

   File "/opt/couchbase/lib/python/cbmgr.py", line 17, in <module>

   from argparse import ArgumentError, ArgumentParser, HelpFormatter, Action, SUPPRESS

   ImportError: bad magic number in 'argparse': b'\x03\xf3\r\n'

   root@ip-172-31-18-93:~

Workaround

Remove all file with extension pyc in /opt/couchbase/lib/python/*.pyc as mention in this Forum, it works

root@ip-172-31-18-93:~# rm -rf /opt/couchbase/lib/python/*.pyc

root@ip-172-31-18-93:~# /opt/couchbase/bin/couchbase-cli bucket-create -c localhost:8091 --username Administrator --password password --bucket bucket2 --bucket-type couchbase --bucket-ramsize 256 --bucket-replica 1 --bucket-priority high --bucket-eviction-policy fullEviction --enable-flush 0 --enable-index-replica 1

SUCCESS: Bucket created

root@ip-172-31-18-93:~#  

This bug does not affect centos as I confirmed in the forum.