PR: Fix Help plugin string validation for the console

[dalthviz]

Description of Changes

• Wrote at least one-line docstrings (for any new functions)
• Added unit test(s) covering the changes (if testable)
• Included a screenshot (if affecting the UI)

Fix validation to correctly check if an object is defined in the shell attached to the Help or current Console.

Issue(s) Resolved

Fixes #9143

Affirmation

By submitting this Pull Request or typing my (user)name below,
I affirm the Developer Certificate of Origin
with respect to all commits and content included in this PR,
and understand I am releasing the same under Spyder's MIT (Expat) license.

I certify the above statement is true and correct: dalthviz

[pep8speaks]

Hello @dalthviz! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2019-04-24 12:02:06 UTC

[ccordoba12]

@dalthviz, I left a minor comment.

Please also add tests to catch the regressions reported on issues #9143 and #8762. Thanks!

[CAM-Gerlach]

Fix validation to correctly check if and object if denifed in the shell attached to the Help or current Console

I think I parsed this correctly and fixed up the various problems, but just letting you know in case I didn't; it was a tad garbled...

[ccordoba12]

@dalthviz, last minor comments, then this should be ready. Thanks!

[ccordoba12]

@dalthviz, this is ready, please don't add more commits here. I'll fix the Azure error and then merge.

[ccordoba12]

Great work here, thanks a lot @dalthviz!