PR: Fix test_shell_execution for macOS

[mrclary]

zsh does not have the -u shell option. macOS can use bash instead of zsh.

Correct execution (via bash) looks like this:

(spy-dev) >> /bin/bash spyder/app/tests/bash_example.sh $(pwd)
allexport      	off
braceexpand    	on
emacs          	off
errexit        	on
errtrace       	off
functrace      	off
hashall        	on
histexpand     	off
history        	off
ignoreeof      	off
interactive-comments	on
keyword        	off
monitor        	off
noclobber      	off
noexec         	off
noglob         	off
nolog          	off
notify         	off
nounset        	off
onecmd         	off
physical       	off
pipefail       	off
posix          	off
privileged     	off
verbose        	off
vi             	off
xtrace         	on
+ TEMP_DIR=/Users/rclary/Documents/Repos/Spyder-IDE/spyder
++ uname
+ echo 'This is a temporary file created by Darwin'

The error from zsh is:

(spy-dev) >> /bin/zsh spyder/app/tests/bash_example.sh $(pwd)
spyder/app/tests/bash_example.sh:set:1: no such option: u

Since zsh is the default macOS shell, -u is removed from bash_example.sh

[mrclary]

@ccordoba12,
Alternatively, the -u option can be removed from bash_example.sh.

https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html

-u
Treat unset variables and parameters other than the special parameters ‘@’ or ‘’, or array variables subscripted with ‘@’ or ‘’, as an error when performing parameter expansion. An error message will be written to the standard error, and a non-interactive shell will exit.

I don't think it is necessary in our case since we do not perform any parameter expansion on unset variables.
Indeed, I don't know that the set command or any of the options are necessary for this test.

[ccordoba12]

Alternatively, the -u option can be removed from bash_example.sh

Ok, please do that instead because we should try to run the test with zsh since it's the default shell on Mac.

[ccordoba12]

Thanks @mrclary!