Changing supported version of tornado to 6.0 and above

[ashu658]

Description

Agent fails to detach context with tornado 5.1.1. The issue comes because contextvars does not work perfectly with tornado's gen.coroutine as mentioned in this issue. contextvars has problems with resetting the context with gen.coroutine. The fix for this is implemented in tornado 6.1

In tornado 5.1.1 _execute is implemented as gen.coroutine link whereas it is converted to a native coroutine in tornado 6 link. contextvars works corretcly with native coroutines. So, changing the supported version for the agent to tornado>=6 solves the issue.

Type of change

• This change requires a documentation update

How Has This Been Tested?

Reproduce the issue: Running instrumented tornado 5.1.1 app with agent throws error. ERROR:opentelemetry.context:Failed to detach context
This error doesn’t come with tornado>=6. Tested by running manually.

Details on the setup to reproduce can be found in the comment thread of the issue #904

Does This PR Require a Core Repo Change?

• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Documentation has been updated

[owais]

While dropping support for 5.x makes sense if we don't support it, it is not really a fix for #904 :)

[ashu658]

Yes, sorry my bad. Removed the fixes statement.

[ocelotl]

This seems to be an issue with Tornado. Unless we can fix or bypass this issue with a commit to this repo that is not dropping support for 5.X.Y (I'd rather have an issue that can happen with a Tornado version rather than to drop support for that version completely), I say we close this issue.