Use serverReadyAction in django/flask to start the web browser

[karthiknadig]

This is a pattern that works for Django/Flask:

            "serverReadyAction": {
                "pattern": ".*(https?:\\/\\/\\S+:[0-9]+\\/?).*",
                "uriFormat": "%s",
                "action": "openExternally"
              }

There is a issue when using subProcess: true. This results in multiple tabs being opened. This is because for every debug adapter it launches a separate tab. we either need to block that, or remove serverReadyAction when we attach to the sub-process.

Full Dajngo config:

        {
            "name": "Django",
            "type": "python",
            "request": "launch",
            "program": "${workspaceFolder}/manage.py",
            "args": [
                "runserver",
                "--noreload",
                "--nothreading"
            ],
            "django": true,
            "serverReadyAction": {
                "pattern": ".*(https?:\\/\\/\\S+:[0-9]+\\/?).*",
                "uriFormat": "%s",
                "action": "openExternally"
              }
        }

Full Flask Config:

        {
            "name": "Flask",
            "type": "python",
            "request": "launch",
            "module": "flask",
            "env": {
                "FLASK_APP": "app.py",
                "FLASK_ENV": "development",
                "FLASK_DEBUG": "0"
            },
            "args": [
                "run",
                "--no-debugger",
                "--no-reload"
            ],
            "jinja": true,
            "serverReadyAction": {
                "pattern": ".*(https?:\\/\\/\\S+:[0-9]+\\/?).*",
                "uriFormat": "%s",
                "action": "openExternally"
              }
        }

[DonJayamanne]

Duplicate of #1058