basic error handling

opt/inject_dbs

@@ -2,7 +2,7 @@
 import os
 import sys
 from lib2to3 import pygram, pytree
-from lib2to3.pgen2 import driver
+from lib2to3.pgen2 import driver, parse
 
 BIN_DIR = os.path.dirname(__file__)
 
@@ -23,9 +23,17 @@ if __name__ == "__main__":
     patch   = os.path.join(BIN_DIR, "dbs.py.src")
 
     drv = driver.Driver(pygram.python_grammar, pytree.convert)
+    try:
         root = drv.parse_file(src)
+    except parse.ParseError, e:
+        print "fatal: could not parse file as Python"
+        sys.exit(1)
 
     node = find(root, pytree.Leaf(1, "DATABASES")) # Find node for DATABASES = { ... }
+    if not node:
+        print "fatal: could not find DATABASES = stmt"
+        sys.exit(1)
+
     end  = node.parent.next_sibling # calculate adjacent sibling
 
     with open(src) as _src: