faber test.report

when I run the `faber test.report` , it shows

```
configuration check results:
has_cxx11 : False (cached)
has_numpy : True (cached)
gxx.link src.boost_python27
gxx.makedep test.injected.d
gxx.compile test.injected.o
gxx.link test.injected_ext
python.run test.injected
running...
Done.
main() should return report_errors()
Aborted (core dumped)

test.injected: FAIL
gxx.makedep test.properties.d
gxx.compile test.properties.o
gxx.link test.properties_ext
python.run test.properties
running...

```
g++: 4.8.5
boost: 1.69.0

----------------------------
it shows `has_cxx11 : False (cached)`, I wonder is it ok to have this False?
although some tests shows PASS
thanks for help！