Change variable order in Python try snippets

By changing the code inside the try block to $0 it is possible to wrap the action region with a
try/except block when yas-wrap-around-region is set to t.

Author: r-darwish

snippets/python-mode/try

@@ -3,6 +3,6 @@
 # key: try
 # --
 try:
-    $1
-except ${2:Exception}:
-    $0
+    $0
+except ${1:Exception}:
+    $2

snippets/python-mode/tryelse

@@ -3,8 +3,8 @@
 # key: try
 # --
 try:
-    $1
-except $2:
-    $3
+    $0
+except $1:
+    $2
 else:
-    $0
+    $3