ensure correct value type in data field of Request object in Python 2/3

[boegel]

Without this fix, the added test fails as below when using Python 3.

This is relevant for features like --upload-test-report.

ERROR: test_restclient (__main__.GithubTest)
Test use of RestClient.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Volumes/work/easybuild-framework/test/framework/github.py", line 575, in test_restclient
    status, body = client.user.emails.post(body='test@example.com')
  File "/Volumes/work/easybuild-framework/easybuild/base/rest.py", line 136, in post
    return self.request(self.POST, url, json.dumps(body), headers, content_type='application/json')
  File "/Volumes/work/easybuild-framework/easybuild/base/rest.py", line 167, in request
    conn = self.get_connection(method, url, body, headers)
  File "/Volumes/work/easybuild-framework/easybuild/base/rest.py", line 201, in get_connection
    connection = self.opener.open(request)
  File "/usr/local/Cellar/python/3.7.2/Frameworks/Python.framework/Versions/3.7/lib/python3.7/urllib/request.py", line 523, in open
    req = meth(req)
  File "/usr/local/Cellar/python/3.7.2/Frameworks/Python.framework/Versions/3.7/lib/python3.7/urllib/request.py", line 1247, in do_request_
    raise TypeError(msg)
TypeError: POST data should be bytes, an iterable of bytes, or a file object. It cannot be of type str.

[wpoely86]

why don't you encode this on the fly instead of this comment?

[boegel]

I stole this from the vsc-base checks, I have to admit I don't know why it was done like this.

Will try and encode on the fly...

[boegel]

fixed in e0e1e16