Add ClientConnectorDNSError for differentiating DNS errors from others

[mstojcevich-cisco]

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What do these changes do?

Adds a ClientConnectorError that's specific to DNS resolution errors. See #8455

Are there changes in behavior for the user?

Existing usages should still keep working the same as before since this extends from ClientConnectorError. Users can now catch ClientConnectorDNSError if they're looking for DNS errors specifically.

Is it a substantial burden for the maintainers to support this?

I can't see this being difficult to maintain since the Resolver abstraction already exists to determine when errors are related to DNS or some other part of the connection.

Related issue number

Fixes #8455

Checklist

• [X] I think the code is well written
• [X] Unit tests for the changes exist
• [X] Documentation reflects the changes
• [X] If you provide code modification, please add yourself to CONTRIBUTORS.txt
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• [X] Add a new news fragment into the CHANGES/ folder

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.59%. Comparing base (216e082) to head (8d309c0). Report is 657 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #8456   +/-   ##
=======================================
  Coverage   98.58%   98.59%           
=======================================
  Files         107      105    -2     
  Lines       35026    35089   +63     
  Branches     4151     4178   +27     
=======================================
+ Hits        34531    34595   +64     
+ Misses        330      329    -1     
  Partials      165      165           

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[webknjaz]

We need to think the DNS-related exception hierarchy through — perhaps it needs a base exception with subtypes. Similar to https://github.com/aio-libs/aiohttp/pull/6722#discussion_r1477103562.

Additionally, the documentation would need to be updated to list the new exceptions with explanations.

[patchback[bot]]

Backport to 3.10: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply b09d7cc07607d01badf8051f5b8feb2a2ed070c8 on top of patchback/backports/3.10/b09d7cc07607d01badf8051f5b8feb2a2ed070c8/pr-8456

Backporting merged PR #8456 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these instructions you'll refer to it by the name upstream. If you don't have it, here's how you can add it:

   $ git remote add upstream https://github.com/aio-libs/aiohttp.git
   

3. Ensure you have the latest copy of upstream and prepare a branch that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.10/b09d7cc07607d01badf8051f5b8feb2a2ed070c8/pr-8456 upstream/3.10
   

4. Now, cherry-pick PR #8456 contents into that branch:

   $ git cherry-pick -x b09d7cc07607d01badf8051f5b8feb2a2ed070c8
   

   If it'll yell at you with something like fatal: Commit b09d7cc07607d01badf8051f5b8feb2a2ed070c8 is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x b09d7cc07607d01badf8051f5b8feb2a2ed070c8
   

5. At this point, you'll probably encounter some merge conflicts. You must resolve them in to preserve the patch from PR #8456 as close to the original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.10/b09d7cc07607d01badf8051f5b8feb2a2ed070c8/pr-8456
   

7. Create a PR, ensure that the CI is green. If it's not — update it so that the tests and any other checks pass. This is it! Now relax and wait for the maintainers to process your pull request when they have some cycles to do reviews. Don't worry — they'll tell you if any improvements are necessary when the time comes!

🤖 @patchback I'm built with octomachinery and my source is open — https://github.com/sanitizers/patchback-github-app.

[patchback[bot]]

Backport to 3.11: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply b09d7cc07607d01badf8051f5b8feb2a2ed070c8 on top of patchback/backports/3.11/b09d7cc07607d01badf8051f5b8feb2a2ed070c8/pr-8456

Backporting merged PR #8456 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these instructions you'll refer to it by the name upstream. If you don't have it, here's how you can add it:

   $ git remote add upstream https://github.com/aio-libs/aiohttp.git
   

3. Ensure you have the latest copy of upstream and prepare a branch that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.11/b09d7cc07607d01badf8051f5b8feb2a2ed070c8/pr-8456 upstream/3.11
   

4. Now, cherry-pick PR #8456 contents into that branch:

   $ git cherry-pick -x b09d7cc07607d01badf8051f5b8feb2a2ed070c8
   

   If it'll yell at you with something like fatal: Commit b09d7cc07607d01badf8051f5b8feb2a2ed070c8 is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x b09d7cc07607d01badf8051f5b8feb2a2ed070c8
   

5. At this point, you'll probably encounter some merge conflicts. You must resolve them in to preserve the patch from PR #8456 as close to the original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.11/b09d7cc07607d01badf8051f5b8feb2a2ed070c8/pr-8456
   

7. Create a PR, ensure that the CI is green. If it's not — update it so that the tests and any other checks pass. This is it! Now relax and wait for the maintainers to process your pull request when they have some cycles to do reviews. Don't worry — they'll tell you if any improvements are necessary when the time comes!

🤖 @patchback I'm built with octomachinery and my source is open — https://github.com/sanitizers/patchback-github-app.