Transfer Excel data I/O from message_ix

[khaeru]

Replaced by #289.

[khaeru]

@zikolach as of the last commit here (b35889b), tests pass on all platforms and versions except Python 3.6 (i.e. 3.7 passes) on AppVeyor/Windows, where I see:

_________________________ TestScenario.test_excel_io __________________________
self = <test_scenario.TestScenario object at 0x000000535186F1D0>
scen = <ixmp.core.Scenario object at 0x000000535185E908>
scen_empty = <ixmp.core.Scenario object at 0x0000005351875438>
tmp_path = WindowsPath('C:/Users/appveyor/AppData/Local/Temp/1/pytest-of-appveyor/pytest-0/test_excel_io1/output.xlsx')
    def test_excel_io(self, scen, scen_empty, tmp_path):
        tmp_path /= 'output.xlsx'
    
        # FIXME remove_solution, check_out, commit, solve, commit should not
        #       be needed to make this small data addition.
        scen.remove_solution()
        scen.check_out()
        # A 1-D set indexed by another set
        scen.init_set('foo', 'j')
        scen.add_set('foo', [['new-york'], ['topeka']])
        # A scalar parameter with unusual units
        scen.platform.add_unit('pounds')
        scen.init_scalar('bar', 100, 'pounds')
        scen.commit('')
        scen.solve()
    
        # Solved Scenario can be written to file
        scen.to_excel(tmp_path)
    
        # With init_items=False, can't be read into an empty Scenario
        with pytest.raises(ValueError, match="no set 'i'; "
                                             "try init_items=True"):
            scen_empty.read_excel(tmp_path)
    
        # File can be read with init_items=False
>       scen_empty.read_excel(tmp_path, init_items=True, commit_steps=True)
..\..\ixmp\tests\core\test_scenario.py:221: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
..\..\ixmp\core.py:1515: in read_excel
    commit_steps=commit_steps,
..\..\ixmp\backend\jdbc.py:307: in read_file
    super().read_file(path, item_type, **kwargs)
..\..\ixmp\backend\base.py:274: in read_file
    s_read_excel(self, s, path, **kwargs)
..\..\ixmp\backend\io.py:178: in s_read_excel
    s.commit(f'Loaded sets from {path}')
..\..\ixmp\core.py:441: in commit
    self._backend('commit', comment)
..\..\ixmp\core.py:417: in _backend
    return self.platform._backend(self, method, *args, **kwargs)
..\..\ixmp\backend\base.py:22: in __call__
    return getattr(self, method)(obj, *args, **kwargs)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
self = <ixmp.backend.jdbc.JDBCBackend object at 0x00000053523EBE10>
ts = <ixmp.core.Scenario object at 0x0000005351875438>
comment = 'Loaded sets from C:\\Users\\appveyor\\AppData\\Local\\Temp\\1\\pytest-of-appveyor\\pytest-0\\test_excel_io1\\output.xlsx'
    def commit(self, ts, comment):
>       self.jindex[ts].commit(comment)
E       jpype._jclass.at.ac.iiasa.ixmp.exceptions.IxException: at.ac.iiasa.ixmp.exceptions.IxException: Wrong status AVAILABLE_IN_DB specified for run -1 or run not found!
..\..\ixmp\backend\jdbc.py:450: at.ac.iiasa.ixmp.exceptions.IxException

Do you have any intuition about what this means or why it only occurs in this one circumstance? I've tried restarting the test, but same result.

[zikolach]

@khaeru it looks strange, based on exception we can conclude that scenario was not saved to DB (run id equals -1) when it calls checkIn method (as final step of commit call, when scenario should be already committed). In principle that is only possible when something went wrong committing scenario and failed in exception block, but then we should see message There was a problem writing data to the database with stack trace in the output. Could it be that pytest somehow hides/truncates the output?

[zikolach]

Updated jar. Let's see what the output will be now

[khaeru]

Closing in favour of #289.