[SPARK-2627] it's PEP 8, not PEP8

Minor, I know.

Author: nchammas

dev/lint-python

@@ -32,10 +32,10 @@ pep8_status=${PIPESTATUS[0]} #$?
 
 if [ $pep8_status -ne 0 ]
     then
-        echo "PEP8 checks failed."
+        echo "PEP 8 checks failed."
         cat "$PEP8_REPORT_PATH"
     else
-        echo "PEP8 checks passed."
+        echo "PEP 8 checks passed."
 fi
 
 rm -f "$PEP8_REPORT_PATH"