[pypy-issue] Issue #2776: pip crashes if MALLOC_CHECK_ is set (pypy/pypy)

[Christoph Reiter]

New issue 2776: pip crashes if MALLOC_CHECK_ is set
https://bitbucket.org/pypy/pypy/issues/2776/pip-crashes-if-malloc_check_-is-set

Christoph Reiter:

```
MALLOC_CHECK_=3 pypy -m pip
*** Error in `python': free(): invalid pointer: 0x0000000000f9a890 ***
Aborted (core dumped)
```