Merge pull request #225 from johnmcdonnell/pymc3

More interpretable error when scikits.sparse is missing.

Author: twiecki

pymc/distributions/continuous.py

@@ -102,7 +102,7 @@ def logp(value):
     mode = mean
 
     logp.__doc__ = """
-        Normal log-likelihood with paraemters mu={0} and tau={1}.
+        Normal log-likelihood with parameters mu={0} and tau={1}.
         
         Parameters
         ----------

pymc/step_methods/quadpotential.py

@@ -13,6 +13,8 @@ def quad_potential(C, is_cov):
         return C
 
     if issparse(C):
+        if not chol_available:
+            raise ImportError, "Requires scikits.sparse"
         return QuadPotential_SparseInv(C)
 
     partial_check_positive_definite(C)