CI: Check for whitespaces before class (pandas-dev#28489)

Author: Ayowolet

ci/code_checks.sh

@@ -190,6 +190,10 @@ if [[ -z "$CHECK" || "$CHECK" == "patterns" ]]; then
     invgrep -R --include="*.rst" ".. ipython ::" doc/source
     RET=$(($RET + $?)) ; echo $MSG "DONE"
 
+    MSG='Check for extra blank lines after the class definition' ; echo $MSG
+    invgrep -R --include="*.py" --include="*.pyx" -E 'class.*:\n\n( )+"""' .
+    RET=$(($RET + $?)) ; echo $MSG "DONE"
+
     MSG='Check that no file in the repo contains trailing whitespaces' ; echo $MSG
     set -o pipefail
     if [[ "$AZURE" == "true" ]]; then