style: Fix PEP8 blank lines issues in Python files

Done with `autopep8 --select=E3,W3`, fixes:

- E301 - Add missing blank line.
- E302 - Add missing 2 blank lines.
- E303 - Remove extra blank lines.
- E304 - Remove blank line following function decorator.
- E309 - Add missing blank line.
- W391 - Remove trailing blank lines.

doc/tools/makerst.py

@@ -24,6 +24,7 @@ def validate_tag(elem, tag):
 class_names = []
 classes = {}
 
+
 def ul_string(str, ul):
     str += "\n"
     for i in range(len(str) - 1):
@@ -31,6 +32,7 @@ def ul_string(str, ul):
     str += "\n"
     return str
 
+
 def make_class_list(class_list, columns):
 
     f = codecs.open('class_list.rst', 'wb', 'utf-8')
@@ -343,7 +345,6 @@ def make_heading(title, underline):
     return title + '\n' + underline * len(title) + "\n\n"
 
 
-
 def make_rst_class(node):
 
     name = node.attrib['name']
@@ -375,7 +376,6 @@ def make_rst_class(node):
             else:
                 inh = None
 
-
         f.write("\n\n")
 
     inherited = []
@@ -436,7 +436,6 @@ def make_rst_class(node):
             f.write(sep)
         f.write('\n')
 
-
     events = node.find('signals')
     if events != None and len(list(events)) > 0:
         f.write(make_heading('Signals', '-'))
@@ -516,4 +515,3 @@ class_names.sort()
 for cn in class_names:
     c = classes[cn]
     make_rst_class(c)
-