Show error message in report when daily API rate limit is exceed, instead `No vulnerabilities reported`.

[rahulsprajapati]

Description of the Change

Show error message in report when daily API rate limit is exceed, instead No vulnerabilities reported.

Output of wp vuln status:

Alternate Designs

N/A

Benefits

Fix false positive report: currently we get No vulnerabilities reported for this version of <plugin/theme name> when api limit is exceed which gives user false information.

Possible Drawbacks

N/A

Verification Process

1. Go to wpvulndb.com and create new account
2. Install wp-vulnerability-scanner and set up fresh API key in wp-config
3. Run wp-vulnerability-scanner on a site a until the free quota of 25 is full (1-3 times probably enough usually with a bigger site)
4. Check wpvulndb.com account to see that the quota is indeed full
5. Run call to wpvulndb.com API manually ex:

   curl -H "Authorization: Token token=API_TOKEN" https://wpvulndb.com/api/v3/wordpresses/494

6. Observe that API answers: { "status": "rate limit hit" }
7. Test wp vuln status once more and see that everything looks like its running pretty normally.
8. Checkout this branch and run wp vuln status.
9. You'll now see api limit error.

Checklist:

• [ ] I have read the CONTRIBUTING document.
• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my change.
• [ ] All new and existing tests passed.

Applicable Issues

Closes #41

Changelog Entry

• Fix false positive report for wpvulndb.com API Limit exceed errors.

[jeffpaul]

@davidegreenwald @TheLastCicada pinging you both to see if you want/intend to review this as well or if we're good to merge in and continue towards a release?