there is no exit code in pynvme,pyscsi,pysats

[gao7904]

there is no exit code in pynvme,pyscsi,pysats.

It is always helpful in the use.

[jackeichen]

will look at this.

[jackeichen]

fix in 39ccc57

Here is the exit code:
code: bit 0-3
0: command success
1: non pydiskcmd error
2: command parameters error
3: device operation error
4: command build error
5: command execute error
6: check command return status error
7: check command return data error
...
13: function error
14: user defined error
15: reservd

sub-code: bit 4-7
...