Fixed several typos in the codebase

Change-Id: I66e05e8240cd24bc97a3591ba72023b23985f9c2
diff --git a/tests/test_scheduler.py b/tests/test_scheduler.py
index f66c2fe..d9f9afe 100755
--- a/tests/test_scheduler.py
+++ b/tests/test_scheduler.py
@@ -1127,7 +1127,7 @@
                 raise Exception("Timeout waiting for Zuul to settle")
             # Make sure no new events show up while we're checking
             self.worker.lock.acquire()
-            # have all build states propogated to zuul?
+            # have all build states propagated to zuul?
             if self.haveAllBuildsReported():
                 # Join ensures that the queue is empty _and_ events have been
                 # processed
@@ -2951,10 +2951,10 @@
         statsd = extras.try_import('statsd.statsd')
         statsd.incr('test-incr')
         statsd.timing('test-timing', 3)
-        statsd.gauge('test-guage', 12)
+        statsd.gauge('test-gauge', 12)
         self.assertReportedStat('test-incr', '1|c')
         self.assertReportedStat('test-timing', '3|ms')
-        self.assertReportedStat('test-guage', '12|g')
+        self.assertReportedStat('test-gauge', '12|g')
 
     def test_stuck_job_cleanup(self):
         "Test that pending jobs are cleaned up if removed from layout"
diff --git a/zuul/model.py b/zuul/model.py
index c5c5c7d..884ba09 100644
--- a/zuul/model.py
+++ b/zuul/model.py
@@ -287,7 +287,7 @@
 
 
 class ActionReporter(object):
-    """An ActionReporter has a reporter and its configured paramaters"""
+    """An ActionReporter has a reporter and its configured parameters"""
 
     def __repr__(self):
         return '<ActionReporter %s, %s>' % (self.reporter, self.params)
diff --git a/zuul/scheduler.py b/zuul/scheduler.py
index 55b1624..819bcf3 100644
--- a/zuul/scheduler.py
+++ b/zuul/scheduler.py
@@ -1135,7 +1135,7 @@
 
     def removeChange(self, change):
         # Remove a change from the queue, probably because it has been
-        # superceded by another change.
+        # superseded by another change.
         for item in self.pipeline.getAllItems():
             if item.change == change:
                 self.log.debug("Canceling builds behind change: %s "