So my linux builds generally have a user-config.jam (on Ubuntu 14.04) like:

[...]

using python

: 2.7 # version

: # Interpreter/path to dir

: /usr/include/python2.7 # includes

: /usr/lib/x86_64-linux-gnu # libs

: # conditions

;

using python 

: 3.4 # version

: # Interpreter/path to dir

: /usr/include/python3.4 # includes

: /usr/lib/x86_64-linux-gnu # libs

: # conditions

;

In the last few days, all of my builds have been failing, with b2 complaining at the end:
[...] 

/var/boost/run/boost_bb/src/build/feature.jam:782: in expand-composites from module feature

error: explicitly-specified values of non-free feature <python> conflict

error: existing values: 2.7 3.4

error: value from expanding  <python>3.4 : 3.4

/var/boost/run/boost_bb/src/build/feature.jam:867: in feature.expand from module feature

/var/boost/run/boost_bb/src/build/targets.jam:1070: in evaluate-requirements from module targets

/var/boost/run/boost_bb/src/build/targets.jam:1112: in common-properties2 from module targets

/var/boost/run/boost_bb/src/build/targets.jam:977: in targets.common-properties from module targets

/var/boost/run/boost_bb/src/build/targets.jam:1303: in class@basic-target.generate from module object(alias-target-class

)@2066

/var/boost/run/boost_bb/src/build/targets.jam:774: in generate-really from module object(main-target)@2075

/var/boost/run/boost_bb/src/build/targets.jam:746: in class@main-target.generate from module object(main-target)@2075

/var/boost/run/boost_bb/src/build-system.jam:714: in load from module build-system

/var/boost/run/boost_bb/src/kernel/modules.jam:295: in import from module modules

/var/boost/run/boost_bb/src/kernel/bootstrap.jam:139: in boost-build from module

/var/boost/run/boost_regression/boost-build.jam:57: in module scope from module

# Searching for "process_jam_log" in "/var/boost/run/boost_regression/stage/bin"...

Traceback (most recent call last):

  File "run.py", line 71, in <module>

    runner(root)

  File "/var/boost/run/boost_regression_src/regression.py", line 287, in __init__

    self.main()

  File "/var/boost/run/boost_regression_src/regression.py", line 624, in main

    getattr(self,action_m)()

  File "/var/boost/run/boost_regression_src/regression.py", line 581, in command_regression

    self.command_setup()

  File "/var/boost/run/boost_regression_src/regression.py", line 352, in command_setup

    self.build_if_needed(self.process_jam_log,self.pjl_toolset)

  File "/var/boost/run/boost_regression_src/regression.py", line 715, in build_if_needed

    tool[ 'build_path' ] = self.tool_path( tool )

  File "/var/boost/run/boost_regression_src/regression.py", line 740, in tool_path

    , '\n'.join( [ name_or_spec[ 'path' ], build_dir ] )

Exception: Cannot find "process_jam_log" in any of the following locations:

/var/boost/run/boost_regression/stage/bin/process_jam_log

/var/boost/run/boost_regression/stage/bin

Any thoughts what might be causing this new error?