add examples for errors with/without messages

DEBUG.md

-# How to work with broken programs
-Example: NCL_color_1.py
-Error:
+# Debugging: How to work with broken programs
+What is the Problem? Why debugging? Everything works, right?
+
+## No! Every real world program has errors. Amen
+
+Two options:
+- easy: the program crashes and shows error messages
+- hard: the program seem to work properly, but the results are unexpected
+
+### Example (easy)
+
+Let's take an example of geocat, because they offer so many nice plots: [NCL_color_1.py](./scripts/NCL_color_1.py)
+There should be some nice errors in it, too ;-)
+
+Lessions:
+- Understand your environment and its limitations
+- Read error messages and warning. They are your best friends (most of the time)
+
+An common example of a message hard to understand:
+```python
+print("a = {0}".format(55)
+```
+throws this:
+```shell
+SyntaxError: unexpected EOF while parsing
+```
+Keep it in mind
+
+### Example (hard)
+
+```python
+import sys
+def sum(a,b):
+  return a+b
+
+if __name__ == "__main__":
+  # first some tests
+  print("2 = {0}".format(sum(1,1)))
+  print("5 = {0}".format(sum(1,4)))
+  print("4 = {0}".format(sum(2,2)))
+           
+  # now some user given numbers
+  a = sys.argv[1]
+  b = sys.argv[2]
+  print("a   = {0}".format(a))
+  print("b   = {0}".format(b))
+  print("sum = {0}".format(sum(a,b)))
+```
+### Example (harder)
+
+What should be the result?
+```python
+0.3 == 0.1 + 0.2
+True or False #???
+```
+It's quite obvious, isn't it? Try it!
+
+# 
 Problem: What to do, when the error message is crap
 # printf debugger .. or print