Reintroduce a treshold for PEP8 warnings

To avoid littering the codebase with 'Fix PEP8' commits, we've decided
to reintroduce a treshold so PEP8 fixes can be batched together.

lint.sh

@@ -4,18 +4,21 @@
 #
 # This is run on Travis to ensure that pull requests conform to the project coding standards.
 
+# Ideally, this figure should be 0. But to keep the amount of "Fix PEP8" commits
+# low, we only fail Travis after a certain amount of warnings have accumulated
+THRESHOLD=15
+
 # Run flake8 and convert the output into a format that the "violations" plugin 
-# for Jenkins/Hudson can understand.  Ignore warnings from migrations we we don't
-# really care about those.
+# for Jenkins/Hudson can understand.
+# flake8 is configured in [flake8] section in tox.ini
 ERROR_FILE="violations.txt"
-THRESHOLD=0
-flake8 --max-complexity=10 oscar | perl -ple "s/: /: [E] /" > $ERROR_FILE
+flake8 oscar | perl -ple "s/: /: [E] /" > $ERROR_FILE
+cat $ERROR_FILE
 
 # Check that the number of violations is acceptable
 NUMERRORS=`cat $ERROR_FILE | wc -l`
 if [ $NUMERRORS -gt $THRESHOLD ]
 then
-    echo "The following flake8 errors need to be fixed"
-    cat $ERROR_FILE
+    echo "Too many flake8 errors - maximum allowed is $THRESHOLD, found $NUMERRORS"
     exit 1
 fi