Move antlr version choice out of setup.py

Purpose:
Restore vanilla setup.py so it doesn't clash with automated updates

Change:
Moved antlr version choice logic to compile.py, the first place antlr is loaded
symlink manipulation based on __file__ rather than cwd for dependability

Change-Id: I790e871a40a624da1ca4c60c5f7e73c31e96a18b

congress/datalog/compile.py

@@ -22,18 +22,31 @@ import uuid
 import six
 from six.moves import range
 
-import antlr3
-
 from oslo_log import log as logging
 
 from congress.datalog import analysis
 from congress.datalog.builtin import congressbuiltin
+
+# set up appropriate antlr symlinks and import
+import os
+_congressDir = os.path.dirname(
+    os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+if os.path.islink(_congressDir + "/antlr3"):
+    os.remove(_congressDir + "/antlr3")  # remove existing symlink
 if six.PY2:
+    os.symlink(_congressDir +
+               "/thirdparty/antlr3-antlr-3.5/runtime/Python/antlr3/",
+               _congressDir + "/antlr3")
     from congress.datalog.Python2 import CongressLexer
     from congress.datalog.Python2 import CongressParser
 else:
+    os.symlink(_congressDir +
+               "/thirdparty/antlr3-antlr-3.5/runtime/Python3/antlr3/",
+               _congressDir + "/antlr3")
     from congress.datalog.Python3 import CongressLexer
     from congress.datalog.Python3 import CongressParser
+import antlr3
+
 from congress.datalog import utility
 from congress import exception
 from congress import utils

setup.py

@@ -24,19 +24,6 @@ try:
 except ImportError:
     pass
 
-import os
-import six
-
-# Remove existing symlink
-if os.path.islink("antlr3"):
-    os.remove("antlr3")
-
-# Add appropriate symlink
-if six.PY2:
-    os.symlink("thirdparty/antlr3-antlr-3.5/runtime/Python/antlr3/", "antlr3")
-else:
-    os.symlink("thirdparty/antlr3-antlr-3.5/runtime/Python3/antlr3/", "antlr3")
-
 setuptools.setup(
     setup_requires=['pbr>=1.8'],
     pbr=True)