project: drop Python 3.7 support

[RaitoBezarius]

This removes any Python 3.7 support and bumps it to 3.8 minimum as 3.7 is EOL.

As asked in #973.

Checklist

• All new and existing tests are passing
• (If adding features:) I have added tests to cover my changes
• (If docs changes needed:) I have updated the documentation accordingly.
• I have added an entry to CHANGES.rst because this is a user-facing change or an important bugfix
• I have written proper commit message(s)
  

What changes does this Pull Request introduce?

...

Why is this necessary?

...

[ix5]

For posterity, you should mention the reason for bumping the Python version: werkzeug version 2.3.0 and later drop support for Python 3.7 (see changelog)

We're not dropping that version because of support EOL but because your other PR requires it.

[RaitoBezarius]

For posterity, you should mention the reason for bumping the Python version: werkzeug version 2.3.0 and later drop support for Python 3.7 (see changelog)

We're not dropping that version because of support EOL but because your other PR requires it.

I mean, the root cause is 3.7 has reached EOL in support and security, everyone is dropping it for that reason. The other PR, at its root reason for why it exists, is because 3.7 has been removed.