[pypy-issue] Issue #1933: BareBoneArrayDefNode.access_expr_varindex, incorrect string formatting (pypy/pypy)

[Andrey Churin]

New issue 1933: BareBoneArrayDefNode.access_expr_varindex, incorrect string formatting
https://bitbucket.org/pypy/pypy/issue/1933/barebonearraydefnodeaccess_expr_varindex

Andrey Churin:

rpython/translator/c/node.py (line 345 - 347)

```
#!python
class BareBoneArrayDefNode(NodeWithDependencies):
    ...
    def access_expr(self, baseexpr, index):
        return '%s[%d]' % (baseexpr, index)
    access_expr_varindex = access_expr
    ...
```
here only number is allowed, but index can be a string (for access_expr_varindex)