old_contents: from sympy.solvers import solve
  from sympy.simplify import simplify
  
  
  def singularities(expr, sym):
      """
      Finds singularities for a function.
      Currently supported functions are:
      - univariate real rational functions
  
      Examples
      ========
  
      >>> from sympy.calculus.singularities import singularities
      >>> from sympy import Symbol
      >>> x = Symbol('x', real=True)
      >>> singularities(x**2 + x + 1, x)
      ()
      >>> singularities(1/(x + 1), x)
      (-1,)
  
      References
      ==========
  
      .. [1] http://en.wikipedia.org/wiki/Mathematical_singularity
  
      """
      if not expr.is_rational_function(sym):
          raise NotImplementedError("Algorithms finding singularities for"
                                    " non rational functions are not yet"
                                    " implemented")
      else:
          return tuple(sorted(solve(simplify(1/expr), sym)))
  
new_contents: from sympy.solvers import solve
  from sympy.solvers.solveset import solveset
  from sympy.simplify import simplify
  
  
  def singularities(expr, sym):
      """
      Finds singularities for a function.
      Currently supported functions are:
      - univariate real rational functions
  
      Examples
      ========
  
      >>> from sympy.calculus.singularities import singularities
      >>> from sympy import Symbol
      >>> x = Symbol('x', real=True)
      >>> singularities(x**2 + x + 1, x)
      ()
      >>> singularities(1/(x + 1), x)
      (-1,)
  
      References
      ==========
  
      .. [1] http://en.wikipedia.org/wiki/Mathematical_singularity
  
      """
      if not expr.is_rational_function(sym):
          raise NotImplementedError("Algorithms finding singularities for"
                                    " non rational functions are not yet"
                                    " implemented")
      else:
          return tuple(sorted(solveset(simplify(1/expr), sym)))
  
subject: Replace solve with solveset in sympy.calculus