Using sh library with grep command

[Luca]

I'm trying to use sh (https://pypi.python.org/pypi/sh) for calling
system grep command but it's now working as expected.

An example:

    import sh
    sh.grep('abc', os.getcwd(), '-r')

But I get the ErrorReturnCode_1: exception, that I learned is the
normal exit code for grep command when it not found any match.

The error instance object reported that the command run is:

    *** ErrorReturnCode_1:
      RAN: '/usr/bin/grep abc /Users/keul/test_sh'

Obviously manually running the command I get some output and exit code 0.

Where I'm wrong?

-- 
-- luca

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