Adds hash table write error alert.
Adds hash table write error alert.

Writing can silently fail on certain systems (like mine).  I don't know how to prevent it, but here's a few lines to add in error alerts.
ged-lab/khmer,Winterflower/khmer,Winterflower/khmer,kdmurray91/khmer,F1000Research/khmer,kdmurray91/khmer,jas14/khmer,kdmurray91/khmer,ged-lab/khmer,F1000Research/khmer,souravsingh/khmer,F1000Research/khmer,ged-lab/khmer,jas14/khmer,Winterflower/khmer,jas14/khmer,souravsingh/khmer,souravsingh/khmer