tweet-releasenotes.sh does not check env variables

[romani]

✔ ~/java/github/checkstyle/checkstyle [master|✔] 
$ ./.ci/tweet-releasenotes.sh 
fatal: destination path 'contribution' already exists and is not an empty directory.
^C

expected: failure that varaibles are not defined.

[Rahulkhinchi03]

I still think we should use:

checkForVariable() {
  if [[ "$(declare -p "$1")" =~ ^declare\ -x ]]; then
    echo "Error: Define $1 environment variable"
    exit 1
  fi
}

[romani]

fix is https://stackoverflow.com/questions/65705411/bash-conditional-expression-v-to-check-if-a-variable-is-set

[romani]

Fix is merged