Issue #202: Question: How to create a python package for a price source? (blais/beancount)

[vonpupp]

New issue 202: Question: How to create a python package for a price source?
https://bitbucket.org/blais/beancount/issues/202/question-how-to-create-a-python-package

vonpupp:

Hi,

I have created a custom price source that seems to work fine, however I would like to be able to create a package for it so it can be easily distributed and maintained without messing with beancount source code.

Currently I have the following package skeleton (I used cookicutter)
```
.
├── beancount_cryptocompare
│ ├── cryptocompareusd.py
│ └── __pycache__
│ ├── cryptocompareusd.cpython-36.pyc
│ └── __init__.cpython-36.pyc
├── beancount_cryptocompare.egg-info
│ ├── dependency_links.txt
│ ├── not-zip-safe
│ ├── PKG-INFO
│ ├── requires.txt
│ ├── SOURCES.txt
│ └── top_level.txt
├── ...
├── setup.cfg
├── setup.py
```

When I run a python shell and `import beancount_cryptocompare.cryptocompareusd` it doesn't complain, however when I use the namespace on the price attribute it doesn't work, example:

```
(.env3) > $ bean-price -e USD:cryptocompareusd/ETH --no-cache
Traceback (most recent call last):
File "/usr/lib/python3.6/site-packages/beancount/prices/find_prices.py", line 147, in import_source
__import__(default_name)
ModuleNotFoundError: No module named 'beancount.prices.sources.cryptocompareusd'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/usr/lib/python3.6/site-packages/beancount/prices/find_prices.py", line 151, in import_source
__import__(module_name)
File "/home/av/repos/crypto/beancount_cryptocompare/beancount_cryptocompare/cryptocompareusd.py", line 10, in <module>
import cryptocompare
ModuleNotFoundError: No module named 'cryptocompare'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/usr/bin/bean-price", line 2, in <module>
from beancount.prices.price import main; main()
File "/usr/lib/python3.6/site-packages/beancount/prices/price.py", line 310, in main
args, jobs, entries = process_args()
File "/usr/lib/python3.6/site-packages/beancount/prices/price.py", line 281, in process_args
psource_map = find_prices.parse_source_map(source_str)
File "/usr/lib/python3.6/site-packages/beancount/prices/find_prices.py", line 99, in parse_source_map
for source_str in source_strs.split(','))
File "/usr/lib/python3.6/site-packages/beancount/prices/find_prices.py", line 99, in <genexpr>
for source_str in source_strs.split(','))
File "/usr/lib/python3.6/site-packages/beancount/prices/find_prices.py", line 124, in parse_single_source
module = import_source(short_module_name)
File "/usr/lib/python3.6/site-packages/beancount/prices/find_prices.py", line 155, in import_source
module_name, exc))
ImportError: Could not find price source module "cryptocompareusd": No module named 'cryptocompare'
```

If I try with the full namespace, it doesn't work either, example:
```
av@sa4 ~/repos/crypto/beancount_cryptocompare [20:54:15]
(.env3) > $ bean-price -e USD:beancount_cryptocompare.cryptocompareusd/ETH --no-cache
usage: bean-price [-h] [-e] [-v] [-d DATE] [-i] [-u] [-c] [-a] [-s] [-n]
[--cache CACHE_FILENAME] [--no-cache] [--clear-cache]
sources [sources ...]
```

From what I understood the `find_prices` works as some sort of plugin importer or similar, is that right?

Could you please help me?

Thank you very much.