weird build fails (2.7.11: io; 3.5.1: datetime)

[Valentin Nechayev]

Hi,
the same system (10.2-RELEASE/amd64), clang as default compiler (but
python ports call for gcc 4.8).

For the newest 2.7.11 port, build shows the following messages:

[...]
===>   Generating temporary packing list
[...]
*** WARNING: renaming "_io" since importing it failed: build/lib.freebsd-10.2-RELEASE-p5-amd64-2.7/_io.so: Undefined symbol "_PyCodecInfo_GetIncrementalEncoder"
[...]
Failed to build these modules:
_io

then, it doesn't stop, but "successfully" installs to the stage directory.
Later on, an old port is removed, the new one fails during
installation, and system becomes without python27 port at all (so I
have to restore it from portmaster backup).
I can't found any deeper details in the log why the called symbol is
missing.

Very similar error, with the only difference in symbol name, occurs
with python 3.5.1:

*** WARNING: renaming "_datetime" since importing it failed: build/lib.freebsd-10.2-RELEASE-p5-amd64-3.5/_datetime.so: Undefined symbol "_PyTime_AsTimevalTime_t"
[...]
Following modules built successfully but were removed because they could not be imported:
_datetime

and, again, stage tree installer doesn't see any problem, and upgrade
fails during package replacing.

These errors are stable for the current ports tree and this system.

What to dig?


-netch-