Assorted error handling fixes

[adekbadek]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Adds error handling in a few places to avoid triggering PHP Fatals, and updates the tests so they don't rely on network.

• Improves handling of a variable. Newspack_Newsletters_Constant_Contact_SDK::get_contact can return false or WP_Error in case of failure, and the upsert_contact method was not handling the latter case.
• Improves error handling of Mailchimp usage reports, if the API key is not provided
• Updates the test_render_embed_blocks test not to rely on the network
• Improves error handling in ActiveCampaign usage reports, in case of a network error
• Fixes the failed CI builds (perf: remove CodeMirror/CSSLint to reduce bundle size & speed #1642)

Submitting as a hotfix because the lack of error handling triggers PHP Fatals, which pollute our logs.

How to test the changes in this Pull Request:

• Smoke test, this should be self-explanatory.
• Observe all tests are passing

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 3 lines in your changes missing coverage. Please review.

Project coverage is 19.65%. Comparing base (b245716) to head (94c3748).
Report is 71 commits behind head on release.

Files with missing lines	Patch %	Lines
...pack-newsletters-active-campaign-usage-reports.php	66.66%	1 Missing ⚠️
...lass-newspack-newsletters-constant-contact-sdk.php	0.00%	1 Missing ⚠️
...s-newspack-newsletters-mailchimp-usage-reports.php	50.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             release    #1641      +/-   ##
=============================================
+ Coverage      17.74%   19.65%   +1.90%     
- Complexity      2316     2375      +59     
=============================================
  Files             43       45       +2     
  Lines           8758     8930     +172     
=============================================
+ Hits            1554     1755     +201     
+ Misses          7204     7175      -29     

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[leogermani]

Nice.

I also see these errors when running tests. Not introduced by this PR, just sharing because it seems related

wp_die() called
Message: Error retrieving Mailchimp campaign.
Title: WordPress › Error
Args:
	response: 500
	code: wp_die
	exit: 1
	back_link: 
	link_url: 
	link_text: 
	text_direction: ltr
	charset: UTF-8
	additional_errors: array (
)
	newspack_newsletters_mailchimp_error: 

[dkoo]

@adekbadek @leogermani please look at #1642 to see if this fixes the timeouts we've been seeing on the release and build-distributable jobs.

[adekbadek]

@leogermani – the tests issue should also be resolved by this PR. In the last few failed CI test-php jobs, the offending test was test_render_embed_blocks, which is fixed here.

[matticbot]

🎉 This PR is included in version 3.1.1 🎉

The release is available on GitHub release

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[matticbot]

🎉 This PR is included in version 3.2.0-alpha.2 🎉

The release is available on GitHub release

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