math/py-sympy: Update to 1.5

Breaking changes:

- Deprecate is_EmptySet in favor of is_empty.
- Lambda now requires a tuple rather than a list for the signature
  argument (non-tuple iterables are deprecated)
- Eq(expr) now raises ValueError. Eq(expr, 0) should be used
  instead.
- Refactory of the units module. Scale factors and dimensions are now
  both global and relative to single unit systems.
- get_dixon_matrix() now computes only the necessary monomials for the
  Dixon matrix.
- The ProductSet of no sets is no longer the empty set. Instead is the
  set consisting of the empty tuple.
- Deprecated tensorhead() and tensorsymmetry() static methods.
- Rational, irrational, transcendental and algebraic now imply finite
  in the assumptions system. This means that all symbols declared as
  rational, integer, odd etc are now automatically assumed finite.
- In the (old) assumptions, complex=True now implies finite=True. Note
  that the default assumption for Symbol is complex=None, which allows
  for the possibility for it to be infinite.
- The assumptions system is changed so that only finite numbers can be
  considered real, positive, negative, nonnegative, nonpositive or
  nonzero (since nonzero implies real). This means that any symbol
  declared with e.g. real=True is now automatically considered
  finite. It also means that infinities can not be considered positive
  or negative since they are not real (e.g. oo.is_positive is now
  False).
- New assumptions extended_real, extended_positive etc are added that
  allow for positive and negative infinity. The equivalent of
  Symbol('x', real=True) in version 1.4 is now Symbol('x',
  extended_real=True). The equivalent of Symbol('x', negative=False)
  is now Symbol('x', extended_negative=False) although it is usually
  better to use Symbol('x', nonnegative=True) (which implies both
  real=True and finite=True as well). Code that previously checked if
  x.is_positive should now be written as if x.is_extended_positive if
  it is intended that infinities should be allowed.
- Numbers still compare the same as they do in Python (Float(1) == 1)
  except when they appear in an Expression, e.g. x**2.0 != x**2


(minskim)