Throw or remove `std::runtime_error` exception objects

[knoepfel]

There are a couple places where exception objects are created but not used:

• phlex/plugins/python/src/modulewrap.cpp

  Line 651 in e01f29d

  std::runtime_error("failed to allocate numpy view object"); \

• phlex/plugins/python/src/modulewrap.cpp

  Line 665 in e01f29d

  std::runtime_error("failed to allocate lifeline object"); \

We should either throw these exception objects or not create them.