patch 7.4.1012
Problem:    Vim overwrites the value of $PYTHONHOME.
Solution:   Do not set $PYTHONHOME if it is already set. (Kazuki Sakamoto,
            closes #500)
diff --git a/src/version.c b/src/version.c
index 4023711..badcf25 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1012,
+/**/
     1011,
 /**/
     1010,