Distribution repo rules don't accept some RegEx characters

Distribution repo rules don't accept RegEx characters for mandatory repository field
To Reproduce:
1.Create Distribution repository
2. Go to Rules tab
3. Under "Bintray Output: Repository" attempt to enter any valid RegEx as described in our documentation (https://www.jfrog.com/confluence/display/RTF/Distribution+Repository).
You will not be able to save the rule and receive error:
Illegal character. Use only lowercase letter, numbers or the following characters - _ .