Problem with generate_expression() in Python3.6

[ghackebeil]

So far, I'm only seeing a problem when the summation function is used in an inequality expression. Example:

from pyomo.environ import *

model = ConcreteModel()
model.x = Var([1,2])
model.c = Constraint(expr= summation(model.x) >= 1)

This produces the following error:

  File "~/pyomo/core/base/expr_coopr3.py", line 1376, in _generate_relational_expression__clone_if_needed
    % ( count, ))
RuntimeError: Expression entered generate_relational_expression() with too few references (-1<0); this is indicative of a SERIOUS ERROR in the expression reuse detection scheme.

[greatestape]

I ran into this error running the transport example on 3.6

[aknaut]

I also ran into this error running the knapsack conrete example on a new Python 3.6.0 :: Anaconda 4.3.1 (64-bit) installation

[ghackebeil]

For anyone coming across this issue, we have made a fix on master. Full support for Python 3.6 will be in the next release (hopefully sometime soon).

[ghackebeil]

Fixed in 141c86e