exception handling for model related API (#957)
exception handling for model related API (#957)



Former-commit-id: 719413aa7a198fa4f091951af2688e195b94f53c
shuheik/dynet,clab/dynet,shuheik/dynet,danielhers/dynet,clab/dynet,clab/cnn,shuheik/dynet,xunzhang/dynet,clab/dynet,xunzhang/dynet,shuheik/dynet,clab/dynet,xunzhang/dynet,danielhers/dynet,danielhers/dynet,clab/cnn,clab/dynet,clab/cnn,chunyang-wen/dynet,chunyang-wen/dynet,chunyang-wen/dynet,chunyang-wen/dynet,shuheik/dynet,shuheik/dynet,danielhers/dynet,xunzhang/dynet,danielhers/dynet,clab/dynet,clab/dynet,shuheik/dynet,danielhers/dynet,danielhers/dynet