Getting an error when i try to use wpscan 'could not find gem...'

Hey guys, after run apt-get update my wpscan tool just crashed and now is returning me this error when i try to do some work.

http://imageshack.com/a/img196/7460/r30a.png

i tried some solutions that i found in google but i cant solve this problem.I really appreciate some help !

The best way to fix gem issue in Kali Linux is simply by updating and upgrading:

1. Code:

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   apt-get update

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2. Code:

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   apt-get upgrade -y

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3. Code:

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   apt-get dist-upgrade -y

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The summary from all these Google search pretty much refers to downloading gem package and updating wpscan. apt-get upgrade and dist-upgrade does exactly that. Hope it fixes your problem.
p.s. you should use Kali default repository for update/upgrade etc.