DPCTLSyclInterface should avoid functions that print to std::cout

[oleksandr-pavlyk]

The stream std::cout that the library writes to in a function like
DPCTLDeviceMgr_PrintDeviceInfo is not the same as Python's sys.stdout.

It makes it difficult to verify that printed output is what should be
expected.

Used OutputGrabber class to try to capture std::cout outputs of DPCTLSyclInterface.
The class is implemented in new test/_redirector.py file.

The changes in this commit allow the test to pass, while ensuring
that the captured output is non-empty, but pytest must be envoked with
--capture=no option.

It works as follows:

(idp) [14:36:03 ansatnuc04 dpctl]$ ipython
Python 3.7.10 (default, Jun  4 2021, 06:52:02)
Type 'copyright', 'credits' or 'license' for more information
IPython 7.25.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: import dpctl

In [2]: q = dpctl.SyclQueue()

In [3]: q.print_device_info()
    Name            Intel(R) UHD Graphics [0x9bca]
    Driver version  1.1.20389
    Vendor          Intel(R) Corporation
    Profile         FULL_PROFILE
    Filter string   level_zero:gpu:0

In [4]: import tests._redirector

In [5]: out = tests._redirector.OutputGrabber()

In [6]: with out: q.print_device_info()

In [7]: out.capturedtext
Out[7]: '    Name            Intel(R) UHD Graphics [0x9bca]\n    Driver version  1.1.20389\n    Vendor          Intel(R) Corporation\n    Profile         FULL_PROFILE\n    Filter string   level_zero:gpu:0\n'

It is all good, but In[3] for needed for Out[7] to be non-empty.

(idp) [14:38:36 ansatnuc04 dpctl]$ ipython
Python 3.7.10 (default, Jun  4 2021, 06:52:02)
Type 'copyright', 'credits' or 'license' for more information
IPython 7.25.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: import dpctl

In [2]: q = dpctl.SyclQueue()

In [3]: import tests._redirector

In [4]: out = tests._redirector.OutputGrabber()

In [5]: with out: q.print_device_info()

In [6]: out.capturedtext
Out[6]: ''

This is because libDPCTLSyclInterface does not initialize std::cout, and In[5] writes into a different std::cout that output grabber captured.

[oleksandr-pavlyk]

I just pushed a change to use function added in #620 . Once that is merged, this becomes ready for review.

[coveralls]

Coverage increased (+0.01%) to 74.424% when pulling b6e7e23 on cleanup/test_sycl_queue into 782340f on master.

[oleksandr-pavlyk]

OS sycl bundle from 2021-10-06 does not contain CL/sycl/version.hpp instance of template CL/sycl/version.hpp.in, so please disregard that failure.

[diptorupd]

Unless you want to wait for TeamCity to finish, feel free to merge.

[oleksandr-pavlyk]

I ended up removing use of OutputGrabber in favor of pytest's own stream capture fixture. Since Python API only outputs to Python's stream, pytest works well and there is no need for the OutputGrabber .