setup: use try/except/finally

This will raise a syntax error for people who attempt to use Py2.4,
but that's already going to fail and we have no way to keep other
2.6isms from creeping in since we've removed the check-code rules and
the buildbot.

setup.py

@@ -106,25 +106,24 b' def hasfunction(cc, funcname):'
     tmpdir = tempfile.mkdtemp(prefix='hg-install-')
     devnull = oldstderr = None
     try:
-        try:
-            fname = os.path.join(tmpdir, 'funcname.c')
-            f = open(fname, 'w')
-            f.write('int main(void) {\n')
-            f.write('    %s();\n' % funcname)
-            f.write('}\n')
-            f.close()
-            # Redirect stderr to /dev/null to hide any error messages
-            # from the compiler.
-            # This will have to be changed if we ever have to check
-            # for a function on Windows.
-            devnull = open('/dev/null', 'w')
-            oldstderr = os.dup(sys.stderr.fileno())
-            os.dup2(devnull.fileno(), sys.stderr.fileno())
-            objects = cc.compile([fname], output_dir=tmpdir)
-            cc.link_executable(objects, os.path.join(tmpdir, "a.out"))
-        except Exception:
-            return False
+        fname = os.path.join(tmpdir, 'funcname.c')
+        f = open(fname, 'w')
+        f.write('int main(void) {\n')
+        f.write('    %s();\n' % funcname)
+        f.write('}\n')
+        f.close()
+        # Redirect stderr to /dev/null to hide any error messages
+        # from the compiler.
+        # This will have to be changed if we ever have to check
+        # for a function on Windows.
+        devnull = open('/dev/null', 'w')
+        oldstderr = os.dup(sys.stderr.fileno())
+        os.dup2(devnull.fileno(), sys.stderr.fileno())
+        objects = cc.compile([fname], output_dir=tmpdir)
+        cc.link_executable(objects, os.path.join(tmpdir, "a.out"))
         return True
+    except Exception:
+        return False
     finally:
         if oldstderr is not None:
             os.dup2(oldstderr, sys.stderr.fileno())