FileExistsError does not exist in Python 2

[raphtown]

FileExistsError was only added in Python 3. If an exception is thrown by mkdir, then the exception is not caught and properly dealt with.

sacred/sacred/observers/file_storage.py

Line 106 in ee8d44f

except FileExistsError: # Catch race conditions

[JarnoRFB]

Thanks for reporting! what would be the exception in Python 2?

[raphtown]

Thanks for the response! Something like OSError I would assume?

See https://stackoverflow.com/questions/20790580/python-specifically-handle-file-exists-exception

[boeddeker]

@onurgu made a fix in #372. It looks that you can only raise a sacred.utils.FileExistsError in py2 but not catch it.

[Qwlouse]

In theory the fix from #372 should work. @raphtown does the problem persist with sacred from the current master?

[boeddeker]

As far as I know, except does something like an isinstance check and this check will fail, when a system function throws an OSError with the error code.
Here an example code to test this statement:

import sys
import os
# from sacred.utils import FileExistsError

if sys.version_info[0] == 2:
    import errno

    class FileExistsError(OSError):
        def __init__(self, msg):
            super(FileExistsError, self).__init__(errno.EEXIST, msg)

try:
	os.mkdir('dummy')
except FileExistsError:
	print('catched')
else:
	print('not catched')

$ python3 sacred_py2_FileExists.py  # create the dir
not catched
$ python3 sacred_py2_FileExists.py  # dir exists
catched
$ python2 sacred_py2_FileExists.py  #  dir exists
Traceback (most recent call last):
  File "sacred_py2_FileExists.py", line 16, in <module>
    os.mkdir('dummy')
OSError: [Errno 17] File exists: 'dummy'