Improved handling of output to terminal and files.

New module file_io which takes care of this.  All output should go
through file_io.write, which encodes it using the appropriate
character encoding.  For output to a temporary file, use "with
file_io.tmpfile('name')".

Moved WorblehatException to new module exc, so all modules can access
it without importing worblehat.

cli/fileformat.py

@@ -1,7 +1,6 @@
 import re
 import types
-
-file_encoding = 'utf8'
+from exc import WorblehatException
 
 # The possible fields for each type of object.
 #
@@ -54,10 +53,13 @@ action_fields = {
         { 'type': 'category',
           'required': ['id'] } }
 
-class CommitFormatSyntaxError(Exception):
+class CommitFormatSyntaxError(WorblehatException):
     def __init__(self, msg, linenr):
-        super(CommitFormatSyntaxError, self).__init__(self, 'Syntax error on line %d: %s' %
-                                                      (linenr, msg))
+        WorblehatException.__init__(self, 'Syntax error on line %d: %s' % (linenr, msg))
+
+class CommitFormatError(WorblehatException):
+    def __init__(self, msg):
+        WorblehatException.__init__(self, msg)
 
 def read_field_value_str(val):
     if val.strip() == '':
@@ -67,7 +69,10 @@ def read_field_value_str(val):
 def read_field_value_int(val):
     if val.strip() == '':
         return None
-    return int(val.strip())
+    try:
+        return int(val.strip())
+    except ValueError, TypeError:
+        raise WorblehatException('%s is not an integer' % val)
 
 def read_field_value_dict(val):
     d = {}
@@ -216,10 +221,9 @@ def write_action(d):
                             'd': write_field_value_dict,
                             'l': write_field_value_list}[ftype]
             lines += field + ':' + value_writer(d[field])
-    return lines.encode(file_encoding)
+    return lines
 
 def write_actionlist(actions):
-    encoding_comment = '# -*- coding: %s -*-\n' % file_encoding
-    return encoding_comment + '\n'.join(map(write_action, actions))
+    return '\n'.join(map(write_action, actions))
 
 # test: print write_actionlist([{'comment':'Foo!\nBar!','action':'new-book','isbn':'434545'},{'action':'edit-book','isbn':'654654745','persons':{'author':['ab','foo'],'illustrator':['moo']}},'This\nis\na\ncomment.',{'action':'edit-category','id':'matematikk','name':'Matematikk','placement':['T10','T11']}])