Add CZMQ version check to installer

pyczmq/__init__.py

@@ -2,6 +2,7 @@
 
 from . import (
     zmq,
+    zsys,
     zctx,
     zsocket,
     zstr,

pyczmq/zsys.py

@@ -0,0 +1,18 @@
+from pyczmq._cffi import C, ffi, cdef
+
+__doc__ = """
+The zsys class provides miscellaneous functions. Only a limited set of
+functions are exposed from the czmq zsys module as many duplicate
+functionality of built-in python types or libraries.
+"""
+
+@cdef('void zsys_version (int *major, int *minor, int *patch);')
+def zsys_version():
+    """
+    Returns the tuple (major, minor, patch) of the current czmq version.
+    """
+    major = ffi.new('int*')
+    minor= ffi.new('int*')
+    patch = ffi.new('int*')
+    C.zsys_version(major, minor, patch)
+    return (major[0], minor[0], patch[0])

setup.py

@@ -5,12 +5,13 @@
 ======
 """
 from pyczmq.zmq import version as zmq_version
+from pyczmq.zsys import zsys_version as czmq_version
 from setuptools import setup, find_packages
 import sys
 
 
-if zmq_version() < (4,0,0):
-    print "ERROR: pyczmq requires libzmq 4.0.0 or later."
+if zmq_version() < (4,0,0) or czmq_version() < (2, 1, 0):
+    print "ERROR: pyczmq requires libzmq 4.0.0 or later and libczmq 2.1.0 or later"
     sys.exit(1)