Fixed contributing import rules conflict
Fixed contributing import rules conflict

There was a conflict between these two rules when importing a third party lib due to the `try-except` with the `logger`:

**Rule 1:**
> The imports are ordered as

> 1. Externals libs (One per line sorted and splitted in python stdlib)
> 2. Imports of `openerp`
> 3. Imports from Odoo modules (rarely, and only if necessary)
> 4. Local imports in the relative form

> Inside these 4 groups, the imported lines are alphabetically sorted.

**Rule 2:** 

> In python files where you use a `import external_dependency_python_N` you will need to add a `try-except` with a debug log.

> ```python
 try:
  import external_dependency_python_N
except ImportError:
  _logger.debug('Can not `import external_dependency_python_N`.')
```
Vauxoo/maintainer-tools,OCA/maintainer-tools,akretion/maintainer-tools,acsone/maintainers-tools,Endika/maintainer-tools,sambathkumarpi/maintainer-tools,Endika/maintainer-tools,Yajo/maintainer-tools,OCA/maintainer-tools,Yajo/maintainer-tools,acsone/maintainer-tools,hbrunn/maintainers-tools,gurneyalex/maintainers-tools,Endika/maintainer-tools,acsone/maintainers-tools,hbrunn/maintainers-tools,vauxoo-dev/maintainer-tools,OCA/maintainer-tools,acsone/maintainer-tools,vauxoo-dev/maintainer-tools,acsone/maintainer-tools,dreispt/maintainer-tools,sambathkumarpi/maintainer-tools,dreispt/maintainer-tools,acsone/maintainers-tools,OCA/maintainer-tools,akretion/maintainer-tools,acsone/maintainer-tools,Yajo/maintainer-tools,Vauxoo/maintainer-tools,Yajo/maintainer-tools,tafaRU/maintainer-tools,tafaRU/maintainer-tools,dreispt/maintainer-tools,vauxoo-dev/maintainer-tools