Set default_type for HeaderBlock text

[fwump38]

Summary

Fixes #851 (at least for the main branch. This change needs to be applied to v3 branch in slack and slack_sdk respective locations)

Category (place an x in each of the [ ])

• slack.web.WebClient (Web API client)
• slack.webhook.WebhookClient (Incoming Webhook, response_url sender)
• slack.web.classes (UI component builders)
• slack.rtm.RTMClient (RTM client)
• Documents
• Others

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run python setup.py validate after making the changes.

[codecov]

Codecov Report

Merging #852 into main will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #852   +/-   ##
=======================================
  Coverage   87.02%   87.02%           
=======================================
  Files          30       30           
  Lines        3800     3800           
  Branches      341      341           
=======================================
  Hits         3307     3307           
  Misses        344      344           
  Partials      149      149           

Impacted Files	Coverage Δ
slack/web/classes/blocks.py	93.77% <100.00%> (ø)

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[fwump38]

Per this comment I tried running:

python setup.py codegen
python setup.py validate

But got errors for both. Also, per the PR, I'm not sure how to apply these changes to the other branch(es) without making a new PR

[seratch]

But got errors for both. Also, per the PR, I'm not sure how to apply these changes to the other branch(es) without making a new PR

@fwump38 Is it possible to share the errors you've encountered? If it's [Errno 54] Connection reset by peer in tests, it's a known issue: #808 Regarding the codegen command, it exists only in v3 branch, so you don't need to run the command. The validate command does the same as part of it.

[seratch]

LGTM

[seratch]

Thanks for fixing this. I will apply the same change to v3 branch.

[fwump38]

The errors I got when running python setup.py validate were user error. I was using the system python instead of a virtualenv python so a bunch of tests were failing. I don't recall what python version they were failing on but they all pass now.