Allow the formatter used in save_to_disk to toss exceptions.

src/calibre/library/save_to_disk.py

@@ -131,7 +131,7 @@ def preprocess_template(template):
         template = template.decode(preferred_encoding, 'replace')
     return template
 
-class SafeFormat(TemplateFormatter):
+class Formatter(TemplateFormatter):
     '''
     Provides a format function that substitutes '' for any missing value
     '''
@@ -225,8 +225,7 @@ def get_components(template, mi, id, timefmt='%b %Y', length=250,
                     format_args[key] = unicode(format_args[key])
                 else:
                     format_args[key] = ''
-    components = SafeFormat().safe_format(template, format_args,
-                                            'G_C-EXCEPTION!', mi)
+    components = Formatter().unsafe_format(template, format_args, mi)
     components = [x.strip() for x in components.split('/')]
     components = [sanitize_func(x) for x in components if x]
     if not components:

src/calibre/utils/formatter.py

@@ -310,7 +310,16 @@ class TemplateFormatter(string.Formatter):
             ans = string.Formatter.vformat(self, fmt, args, kwargs)
         return self.compress_spaces.sub(' ', ans).strip()
 
-    ########## a formatter guaranteed not to throw and exception ############
+    ########## a formatter that throws exceptions ############
+
+    def unsafe_format(self, fmt, kwargs, book):
+        self.kwargs = kwargs
+        self.book = book
+        self.composite_values = {}
+        self.locals = {}
+        return self.vformat(fmt, [], kwargs).strip()
+
+    ########## a formatter guaranteed not to throw an exception ############
 
     def safe_format(self, fmt, kwargs, error_value, book):
         self.kwargs = kwargs