DEV: link with boost_python3 when using Python 3.

Fix build on homebrew with python3.  Avoid cross linking with
boost_python for Python 2.

Author: pavoljuhas

SConstruct

@@ -93,8 +93,8 @@ env.MergeFlags([os.environ.get(n, '') for n in flagnames])
 good_python_flags = lambda n : (
     not isinstance(n, basestring) or
     not re.match(r'(-g|-Wstrict-prototypes|-O\d)$', n))
-pyver = pyoutput('import sys; print("%i.%i" % sys.version_info[:2])')
-pythonconfig = 'python' + pyver + '-config'
+pyversion = pyoutput('import sys; print("%i.%i" % sys.version_info[:2])')
+pythonconfig = 'python' + pyversion + '-config'
 env.ParseConfig(pythonconfig + " --cflags")
 env.Replace(CCFLAGS=filter(good_python_flags, env['CCFLAGS']))
 env.Replace(CPPDEFINES='')
@@ -145,7 +145,7 @@ if env['profile']:
 
 builddir = env.Dir('build/%s-%s' % (env['build'], platform.machine()))
 
-Export('env', 'pyconfigvar', 'pyoutput')
+Export('env', 'pyconfigvar', 'pyoutput', 'pyversion')
 
 if os.path.isfile('sconscript.local'):
     env.SConscript('sconscript.local')

setup.py

@@ -28,6 +28,8 @@
         'include_dirs' : get_numpy_include_dirs(),
 }
 
+# determine if we run with Python 3.
+PY3 = (sys.version_info[0] == 3)
 
 # Figure out which boost library to use. This doesn't appear to consult
 # LD_LIBRARY_PATH.
@@ -38,7 +40,7 @@ def get_boost_libraries():
     on the system. If required libraries are not found, an Exception will be
     thrown.
     """
-    baselib = "boost_python"
+    baselib = "boost_python3" if PY3 else "boost_python"
     boostlibtags = ['', '-mt'] + ['']
     from ctypes.util import find_library
     for tag in boostlibtags:
@@ -54,7 +56,7 @@ def get_boost_libraries():
         if platform.system() == 'Darwin':
             ldevname = 'DYLD_FALLBACK_LIBRARY_PATH'
         wmsg = ("Cannot detect name suffix for the %r library.  "
-            "Consider setting %s.") % (baselib, ldevname)
+                "Consider setting %s.") % (baselib, ldevname)
         warnings.warn(wmsg)
 
     libs = [lib]
@@ -93,7 +95,7 @@ def gitinfo():
 
 
 def getversioncfg():
-    if sys.version_info[0] >= 3:
+    if PY3:
         from configparser import RawConfigParser
     else:
         from ConfigParser import RawConfigParser

src/extensions/SConscript.configure

@@ -1,4 +1,4 @@
-Import('env', 'pyconfigvar')
+Import('env', 'pyconfigvar', 'pyversion')
 
 # Helper functions -----------------------------------------------------------
 
@@ -11,6 +11,9 @@ def configure_boost_library(libname):
 
     Note: CheckLib function automatically adds library to the environment.
     '''
+    # adjust libname for boost_python
+    if libname == 'boost_python' and pyversion[0] == '3':
+        libname = 'boost_python3'
     # using global conf defined below
     for t in boostlibtags:
         libnamefull = libname + t