Tests fail when run on pytest 5.0.0

[twongCMU]

`On Pytest 4.6.3 the test pass fine but on 5.0.0 some fail:
platform linux -- Python 3.5.2, pytest-5.0.0, py-1.8.0, pluggy-0.12.0

Running tests with Astropy version 3.2.1.
Running tests in stingray docs.

Date: 2019-06-29T13:53:19

Platform: Linux-4.4.0-150-generic-x86_64-with-Ubuntu-16.04-xenial

Executable: /usr/bin/python3

Full Python Version:
3.5.2 (default, Nov 12 2018, 13:43:14)
[GCC 5.4.0 20160609]

encodings: sys: utf-8, locale: UTF-8, filesystem: utf-8
byteorder: little
float info: dig: 15, mant_dig: 15

Numpy: 1.16.4
Scipy: 1.3.0
Matplotlib: 3.0.3
h5py: 2.9.0
Pandas: 0.24.2
astropy_helpers: 3.2.1
Using Astropy options: remote_data: none.

rootdir: /tmp/stingray-test-gaqwq6do/lib/python3.5/site-packages, inifile: setup.cfg
plugins: doctestplus-0.3.0, arraydiff-0.3, remotedata-0.3.1, openfiles-0.3.2

...

====================================================================================================== FAILURES =======================================================================================================
_________________________________________________________________________________________ TestAll.test_phaseogram_bad_weights _________________________________________________________________________________________

self = <stingray.pulse.tests.test_search.TestAll object at 0x7f73361f9400>

def test_phaseogram_bad_weights(self):
    with pytest.raises(ValueError) as excinfo:
        phaseogr, phases, times, additional_info = \
            phaseogram(self.event_times, self.pulse_frequency,
                       weights=[0, 2])

E TypeError: Can't convert 'ExceptionInfo' object to str implicitly

stingray/pulse/tests/test_search.py:47: TypeError
__________________________________________________________________________________ TestAll.test_epoch_folding_search_expocorr_fails ___________________________________________________________________________________

self = <stingray.pulse.tests.test_search.TestAll object at 0x7f732815dba8>

def test_epoch_folding_search_expocorr_fails(self):
    """Test pulse phase calculation, frequency only."""
    frequencies = np.arange(9.8, 9.99, 0.1/self.tseg)
    with pytest.raises(ValueError) as excinfo:
        freq, stat = epoch_folding_search(self.event_times, frequencies,
                                          nbin=23, expocorr=True)

  assert 'To calculate exposure correction' in str(excinfo)

E AssertionError: assert 'To calculate exposure correction' in ''
E + where '' = str()

stingray/pulse/tests/test_search.py:173: AssertionError
_______________________________________________________________________________________ TestAll.test_z_n_search_expocorr_fails ________________________________________________________________________________________

self = <stingray.pulse.tests.test_search.TestAll object at 0x7f73280dbfd0>

def test_z_n_search_expocorr_fails(self):
    """Test pulse phase calculation, frequency only."""
    frequencies = np.arange(9.8, 9.99, 0.1/self.tseg)
    with pytest.raises(ValueError) as excinfo:
        freq, stat = z_n_search(self.event_times, frequencies, nharm=1,
                                nbin=35, expocorr=True)

  assert 'To calculate exposure correction' in str(excinfo)

E AssertionError: assert 'To calculate exposure correction' in ''
E + where '' = str()

stingray/pulse/tests/test_search.py:292: AssertionError
_______________________________________________________________________________________ TestGTI.test_gti_mask_fails_empty_time ________________________________________________________________________________________

self = <stingray.tests.test_gti.TestGTI object at 0x7f73272bf5c0>

def test_gti_mask_fails_empty_time(self):
    arr = np.array([])
    gti = np.array([[0, 2.1], [3.9, 5]])
    with pytest.raises(ValueError) as excinfo:
        create_gti_mask(arr, gti, return_new_gtis=True)

  assert 'empty time array' in str(excinfo)

E AssertionError: assert 'empty time array' in ''
E + where '' = str()

stingray/tests/test_gti.py:67: AssertionError
________________________________________________________________________________________ TestGTI.test_gti_mask_fails_empty_gti ________________________________________________________________________________________

self = <stingray.tests.test_gti.TestGTI object at 0x7f73272c7438>

def test_gti_mask_fails_empty_gti(self):
    arr = np.array([0, 1, 2, 3, 4, 5, 6])
    gti = np.array([])
    with pytest.raises(ValueError) as excinfo:
        create_gti_mask(arr, gti, return_new_gtis=True)

  assert 'empty GTI array' in str(excinfo)

E AssertionError: assert 'empty GTI array' in ''
E + where '' = str()

stingray/tests/test_gti.py:74: AssertionError
_________________________________________________________________________________________ TestGTI.test_check_gti_fails_empty __________________________________________________________________________________________

self = <stingray.tests.test_gti.TestGTI object at 0x7f73272d3710>

def test_check_gti_fails_empty(self):
    with pytest.raises(ValueError) as excinfo:
        check_gtis([])

  assert 'Empty' in str(excinfo)

E AssertionError: assert 'Empty' in ''
E + where '' = str()

stingray/tests/test_gti.py:244: AssertionError
========================================================================== 6 failed, 747 passed, 8 skipped, 7325 warnings in 221.80 seconds ===========================================================================`

[twongCMU]

This happens because in 5.0.0, the exception object does not include the text of the exception, just the type:

<ExceptionInfo ValueError tblen=2>

so when the test looks for a specific substring it doesn't find it. The solution is to print the the .value of the exception to get the full text. I tested this fix on pytest 5.0.0, 4.6.3, and 3.10.1.

[twongCMU]

pytest 5.0.0 was released June 28, 2019.

This issue is the one that caused the tests to fail

[twongCMU]

This fix is affected by StingraySoftware#416 and the temporary hack listed there was used to get the tests passing.