image_getregion returns byte string on Py3

[olaurino]

Originally reported by @nplee on sherpadev.

from the Python 3 build of CIAOX, when "image_getregion" is invoked in Sherpa, a byte string is returned:

sherpa-3> image_getregion()
          b''
sherpa-4> image_getregion().decode()

I didn't have time to reproduce the issue, but I am opening a ticket so it does not fall through the cracks again.

[DougBurke]

This also happens (unsurprisingly) for image_xpaget:

sherpa-1> image_open()
sherpa-2> image_xpaget('version')
          b'sherpa 7.5\n'

[DougBurke]

This does cause problems - e.g. from a session using Python 3.6 where I had added a region to an image, the notice2d_image command fails as shown below (ui is sherpa.astro.ui here):

In [10]: ui.image_getregion()
Out[10]: b'circle(58.716049,55.822531,30.764058);'

In [11]: ui.notice2d_image()
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-11-aa5314fa3698> in <module>()
----> 1 ui.notice2d_image()

<string> in notice2d_image(ids)

/lagado.real/sherpa/sherpa-warnings/sherpa/astro/ui/utils.py in notice2d_image(self, ids)
   6490             if (coord == 'world'):
   6491                 coord = 'wcs'
-> 6492             regions = self.image_getregion(coord).replace(';', '')
   6493             self.notice2d_id(id, regions)
   6494 

TypeError: a bytes-like object is required, not 'str'