incr() on locmem cache resets the expiry time

[Malcolm Box]

On the locmem cache backend, calling incr() causes the key's timeout value to be reset to the default for the cache.

To reproduce:

• setup the default cache to be locmem and with a timeout of 1 second

  cache.set('key', 10, 300)
  time.sleep(1)
  cache.get('key')
  

10

cache.incr('key')
time.sleep(1)
cache.get('key')

None

The cache should still contain the key at the last line.

The problem comes from the implementation of incr() in base.py which uses get() and set() to implement incr(). Since set() is called without a timeout, the cache default time is used.