./hack/redis_install.sh failed to install Redis on ubuntu 20.04

[sonyafenge]

run ./hack/redis_install.sh on ubuntu20.04, got error as below:

The following packages have unmet dependencies:
 redis : Depends: redis-server (< 6:7.0.0-1rl1~focal1.1~) but 6:7.0.2-1rl1~focal1 is to be installed
E: Unable to correct problems, you have held broken packages.
End to install on Ubuntu ......

2. Enable and Run Redis ......
===============================
ls: cannot access '/etc/redis/redis.conf': No such file or directory
sed: can't read /etc/redis/redis.conf: No such file or directory
grep: /etc/redis/redis.conf: No such file or directory
sed: can't read /etc/redis/redis.conf: No such file or directory
grep: /etc/redis/redis.conf: No such file or directory
Failed to restart redis-server.service: Unit redis-server.service not found.
Unit redis-server.service could not be found.

Sleeping for 5 seconds after Redis installation ......

3. Simply Test Redis ......
===============================
3.1) Test ping ......
./hack/redis_install.sh: line 120: redis-cli: command not found

3.2) Test write key and value ......
./hack/redis_install.sh: line 124: redis-cli: command not found

3.3) Test write queue ......
./hack/redis_install.sh: line 131: redis-cli: command not found

Sleep 5 seconds after Redis tests ...

************************************************************
*                                                          *
* You are successful to install and configure Redis Server *
*                                                          *
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[q131172019]

The PR#61 fixes this issue.