Cleanup use of PY3* in the compiler.

hy/_compat.py

@@ -40,6 +40,7 @@ import sys
 
 PY3 = sys.version_info[0] >= 3
 PY33 = sys.version_info >= (3, 3)
+PY34 = sys.version_info >= (3, 4)
 
 if PY3:
     str_type = str

hy/compiler.py

@@ -39,7 +39,7 @@ from hy.errors import HyCompileError, HyTypeError
 
 import hy.macros
 from hy.macros import require, macroexpand
-from hy._compat import str_type, long_type
+from hy._compat import str_type, long_type, PY33, PY3, PY34
 import hy.importer
 
 import traceback
@@ -77,7 +77,7 @@ _compile_table = {}
 
 
 def ast_str(foobar):
-    if sys.version_info[0] >= 3:
+    if PY3:
         return str(foobar)
 
     try:
@@ -754,7 +754,7 @@ class HyASTCompiler(object):
 
         ret = handler_results
 
-        if sys.version_info >= (3, 3):
+        if PY33:
             # Python 3.3 features a merge of TryExcept+TryFinally into Try.
             return ret + ast.Try(
                 lineno=expr.start_line,
@@ -831,7 +831,7 @@ class HyASTCompiler(object):
                     exceptions,
                     "Exception storage target name must be a symbol.")
 
-            if sys.version_info[0] >= 3:
+            if PY3:
                 # Python3 features a change where the Exception handler
                 # moved the name from a Name() to a pure Python String type.
                 #
@@ -1199,7 +1199,7 @@ class HyASTCompiler(object):
                             optional_vars=thing,
                             body=body.stmts)
 
-        if sys.version_info >= (3, 3):
+        if PY33:
             the_with.items = [ast.withitem(context_expr=ctx.force_expr,
                                            optional_vars=thing)]
 
@@ -1699,7 +1699,7 @@ class HyASTCompiler(object):
         arglist = expression.pop(0)
         ret, args, defaults, stararg, kwargs = self._parse_lambda_list(arglist)
 
-        if sys.version_info >= (3, 4):
+        if PY34:
             # Python 3.4+ requres that args are an ast.arg object, rather
             # than an ast.Name or bare string.
             args = [ast.arg(arg=ast_str(x),