# Failure on symbolic solve

Trying to learn manipulation of symbolic expressions. However when I try this one I get a traceback. Is this a bug, limitation, or user error?

```
x,y,z = var('x y z')
assume(x>0)
assume(y>0)
assume(z>0)
eqn = (x == y**z)
solve(eqn, y)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "_sage_input_68.py", line 10, in <module>
exec compile(u'open("___code___.py","w").write("# -*- coding: utf-8 -*-\\n" + _support_.preparse_worksheet_cell(base64.b64decode("eCx5LHogPSB2YXIoJ3ggeSB6JykKYXNzdW1lKHg+MCkKYXNzdW1lKHk+MCkKYXNzdW1lKHo+MCkKZXFuID0gKHggPT0geSoqeikKc29sdmUoZXFuLCB5KQ=="),globals())+"\\n"); execfile(os.path.abspath("___code___.py"))
File "", line 1, in <module>
File "/tmp/tmpgB4hFo/___code___.py", line 8, in <module>
exec compile(u'solve(eqn, y)
File "", line 1, in <module>
File "/home/sage/sage/local/lib/python2.6/site-packages/sage/symbolic/relation.py", line 619, in solve
ans = f.solve(*args,**kwds)
File "expression.pyx", line 7518, in sage.symbolic.expression.Expression.solve (sage/symbolic/expression.cpp:27206)
File "expression.pyx", line 7511, in sage.symbolic.expression.Expression.solve (sage/symbolic/expression.cpp:27084)
File "/home/sage/sage/local/lib/python2.6/site-packages/sage/interfaces/expect.py", line 1474, in __call__
return self._obj.parent().function_call(self._name, [self._obj] + list(args), kwds)
File "/home/sage/sage/local/lib/python2.6/site-packages/sage/interfaces/expect.py", line 1373, in function_call
return self.new(s)
File "/home/sage/sage/local/lib/python2.6/site-packages/sage/interfaces/expect.py", line 1154, in new
return self(code)
File "/home/sage/sage/local/lib/python2.6/site-packages/sage/interfaces/expect.py", line 1090, in __call__
return cls(self, x, name=name)
File "/home/sage/sage/local/lib/python2.6/site-packages/sage/interfaces/expect.py", line 1517, in __init__
raise TypeError, x
TypeError: Computation failed since Maxima requested additional constraints (try the command 'assume(>0)' before integral or limit evaluation, for example):
Is z an integer?
```