add a test which checks the syntax of the pylib on various python versions

--HG--
branch : trunk

py/_testing/check_compile.py

@@ -0,0 +1,10 @@
+import sys
+
+fn = sys.argv[1]
+print("Testing %s" % (fn,))
+fp = open(fn, "rb")
+try:
+    source = fp.read()
+finally:
+    fp.close()
+compile(source, fn, "exec")

py/_testing/test_sources.py

@@ -0,0 +1,19 @@
+import os
+import py
+
+
+this_dir = py.path.local(__file__).dirpath()
+_compile_checker = this_dir.join("check_compile.py")
+_py_root = this_dir.join("..")
+del this_dir
+
+@py.test.mark.multi(pyversion=("2.4", "2.5", "2.6", "3.1"))
+def test_syntax(pyversion):
+    executable = py.path.local.sysfind("python" + pyversion)
+    if executable is None:
+        py.test.skip("no python%s found" % (pyversion,))
+    for path, dirs, filenames in os.walk(str(_py_root)):
+        for fn in filenames:
+            if fn.endswith(".py"):
+                full = os.path.join(path, fn)
+                executable.sysexec(_compile_checker, full)