If we don"t `export` the variable, it's not available in subcommand:
MYAPP_SETTINGS=/path/to/config_file; python3 -c "import os; os.environ['MYAPP_SETTINGS']"
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/usr/lib/python3.5/os.py", line 725, in __getitem__
raise KeyError(key) from None
KeyError: 'MYAPP_SETTINGS'
The ';' is the culprit here.