Exception in child process can lead to duplicate process.

[wracoon]

Hi,

When the child process raises exception in the child block (before executing os.execv), due to too general exception handling it can lead to duplication of process which uses sh.
I encountered the following problem because os.chdir() has raised an exception,
due to path passed to _cwd of command did not exist at the time.
Due to general exception handling in my code the rest of my python program is executed twice by
duplicate process.
Example:
try:
sh.git("clone", origin, local_dir, _cwd="nonexistent_path")
except:
Executed twice.

Fix proposal: The whole child process block should be wrapped in
try:
#child
except:
sys.exit(1)

or something similar.

[amoffat]

thanks @wracoon, fixed in release-1.10 branch