Impacted versions: 10.0

Steps to reproduce:
- Install a new language
- Open the language and click on "Deactivate"
![image](https://user-images.githubusercontent.com/6352350/33546866-7b2a9412-d8e2-11e7-818e-6a5be3801dc0.png)

You'll now get a traceback:
![image](https://user-images.githubusercontent.com/6352350/33546831-5ec2581e-d8e2-11e7-8887-08c0443bb1d8.png)

The issue is coming from https://github.com/odoo/odoo/blob/ab52c636c34b6f8b472a3b45ee162824de08fca4/odoo/addons/base/res/res_lang.py#L227


Current behavior:
Expected singleton error.

Expected behavior: Language is deactivated.


odoo/addons/base/res/res_lang.py
"""
    res = []
    saved_count = len(l) 
    for count in counts:
        if not l:
            break
        if count == -1:
            break
        if count == 0:
            while l:
                res.append(l[:saved_count])
                l = l[saved_count:]
            break
        res.append(l[:count])
        l = l[count:]
        saved_count = count
    if l:
        res.append(l)
    return res
intersperse_pat = re.compile('([^0-9]*)([^ ]*)(.*)')
def intersperse(string, counts, separator=''):
    """
    See the asserts below for examples.
    """
    left, rest, right = intersperse_pat.match(string).groups()
    def reverse(s): return s[::-1]
    splits = split(reverse(rest), counts)
    res = separator.join(map(reverse, reverse(splits)))
    return left + res + right, len(splits) > 0 and len(splits) -1 or 0