Issue #189: beancount error in Arch (blais/beancount)

[Jib]

New issue 189: beancount error in Arch
https://bitbucket.org/blais/beancount/issues/189/beancount-error-in-arch

Jib:

When I run a beancount command (or fava) I get an error: for example`$ bean-check Documents/beancount.beancount ` returns

```
Traceback (most recent call last):
File "/usr/bin/bean-check", line 2, in <module>
from beancount.scripts.check import main; main()
File "/usr/lib/python3.6/site-packages/beancount/scripts/check.py", line 39, in main
extra_validations=validation.HARDCORE_VALIDATIONS)
File "/usr/lib/python3.6/site-packages/beancount/loader.py", line 87, in load_file
extra_validations, encoding)
File "/usr/lib/python3.6/site-packages/beancount/loader.py", line 200, in wrapped
result = function(toplevel_filename, *args, **kw)
File "/usr/lib/python3.6/site-packages/beancount/loader.py", line 219, in _load_file
return _load([(filename, True)], *args, **kw)
File "/usr/lib/python3.6/site-packages/beancount/loader.py", line 460, in _load
extra_validations)
File "/usr/lib/python3.6/site-packages/beancount/ops/validation.py", line 395, in validate
new_errors = validation_function(entries, options_map)
File "/usr/lib/python3.6/site-packages/beancount/ops/validation.py", line 348, in validate_check_transaction_balances
"Transaction does not balance: {}".format(residual),
File "/usr/lib/python3.6/site-packages/beancount/core/inventory.py", line 106, in __str__
return self.to_string()
File "/usr/lib/python3.6/site-packages/beancount/core/inventory.py", line 98, in to_string
', '.join(pos.to_string(dformat) for pos in sorted(self)))
File "/usr/lib/python3.6/site-packages/beancount/core/position.py", line 228, in __lt__
return self.sortkey() < other.sortkey()
File "/usr/lib/python3.6/site-packages/beancount/core/position.py", line 210, in sortkey
order_units = CURRENCY_ORDER.get(currency, NCURRENCIES + len(currency))
TypeError: object of type 'type' has no len()
```

This is a new error, I started experiencing it today.

I use Arch, and got beancount from [this AUR package](https://aur.archlinux.org/packages/beancount/).

Any ideas ?