webapp: try not to use pycurl for live trace streaming

[yugangw-msft]

@haoc, for you get ramp up :-)
It would be great to use built-in http modules or the requests to accomplish it, so that we don't need to pull in the pycurl
The code is here

/CC:@derekbekoe

[derekbekoe]

If we are going to use pycurl before our next release, we should add the dependency to our documentation (for the distributions that need it).

[yugangw-msft]

For background, the reason to use pycurl is per kudu's document , which calls out using curl

[haocs]

https://github.com/kennethreitz/requests/issues/3577 Some discussions of the issue that blocks replacing pycurl. Still trying to figure out how to let requests print data chunk by chunk as curl does.

[yugangw-msft]

Appears fixed. Thanks @haocs !