THRIFT-2849: spelling errors fixed using codespell tool

Client: All
Patch: Anatol Pomozov

This closes #281
diff --git a/lib/py/src/server/TNonblockingServer.py b/lib/py/src/server/TNonblockingServer.py
index 4a035b6..39486cd 100644
--- a/lib/py/src/server/TNonblockingServer.py
+++ b/lib/py/src/server/TNonblockingServer.py
@@ -261,7 +261,7 @@
     def wake_up(self):
         """Wake up main thread.
 
-        The server usualy waits in select call in we should terminate one.
+        The server usually waits in select call in we should terminate one.
         The simplest way is using socketpair.
 
         Select always wait to read from the first socket of socketpair.