fix for dummy issue again

.travis.yml

@@ -10,7 +10,7 @@ python:
   - "pypy"
 before_install: 
  - sudo apt-get update -qq
- - sudo apt-get install -qq glpk
+ - sudo apt-get install -qq glpk python-glpk
   #- pip install glpk
   #- sudo apt-get install coinor-cbc
 # command to install dependencies

src/pulp/pulp.py

@@ -1502,7 +1502,7 @@ class LpProblem(object):
                 dummyVar = self.get_dummyVar()
                 constraint += dummyVar
                 #set this dummyvar to zero so infeasible problems are not made feasible
-                f.write((dummyVar == 0.0).asCplexLpConstraint(k))
+                f.write((dummyVar == 0.0).asCplexLpConstraint("_dummy"))
             f.write(constraint.asCplexLpConstraint(k))
         vs = self.variables()
         # check if any names are longer than 100 characters