[core] Add file name and line number to module loading errors.

This should make it easier to debug when the import fails due to some weird error deep inside some module.

willie/bot.py

@@ -262,7 +262,10 @@ def setup(self):
                 module = imp.load_source(name, filename)
             except Exception, e:
                 error_count = error_count + 1
-                stderr("Error loading %s: %s (in bot.py)" % (name, e))
+                filename, lineno = tools.get_raising_file_and_line()
+                rel_path = os.path.relpath(filename, os.path.dirname(__file__))
+                raising_stmt = "%s:%d" % (rel_path, lineno)
+                stderr("Error loading %s: %s (%s)" % (name, e, raising_stmt))
             else:
                 try:
                     if hasattr(module, 'setup'):
@@ -271,8 +274,11 @@ def setup(self):
                     modules.append(name)
                 except Exception, e:
                     error_count = error_count + 1
-                    stderr("Error in %s setup procedure: %s (in bot.py)"
-                           % (name, e))
+                    filename, lineno = tools.get_raising_file_and_line()
+                    rel_path = os.path.relpath(filename, os.path.dirname(__file__))
+                    raising_stmt = "%s:%d" % (rel_path, lineno)
+                    stderr("Error in %s setup procedure: %s (%s)"
+                           % (name, e, raising_stmt))
 
         if modules:
             stderr('\n\nRegistered %d modules,' % (len(modules) - 1))

willie/tools.py

@@ -28,6 +28,19 @@
 import copy
 
 
+def get_raising_file_and_line(tb=None):
+    """Return the file and line number of the statement that raised the tb
+
+    Returns: (filename, lineno) tuple
+    """
+    if not tb:
+        tb = sys.exc_info()[2]
+
+    filename, lineno, _context, _line = traceback.extract_tb(tb)[-1]
+
+    return filename, lineno
+
+
 def get_command_regexp(prefix, command):
     """Return a compiled regexp object that implements the command."""
     # Escape all whitespace with a single backslash. This ensures that regexp