The `from trac.util.translation import _` in trac/core.py was triggering a recursive import of `trac.core.TracError` via `trac/util/__init__.py`:
{{{
...
[error] File "/packages/trac/branches/upstream-trunk/trac/core.py",
line 19, in ?\n from trac.util.translation import _
[error] File "/packages/trac/branches/upstream-trunk/trac/util/__init__.py", line 31, in ?\n from trac.core import TracError
[error] ImportError: cannot import name TracError
}}}
