Update openjdk-7-jre to openjdk-8-jre in Dockerfile

Also adds .pytest_cache to gitignore.

Author: jthomale

.gitignore

@@ -13,6 +13,7 @@ celerybeat-schedule
 django_sierra
 django_sierra_test
 .cache/
+.pytest_cache/
 
 /pids.txt
 /django/sierra/media/*

Dockerfile

@@ -1,7 +1,7 @@
 FROM python:2.7
 
 RUN apt-get update -qq && \
-    apt-get install -y libpq-dev python-dev mysql-client netcat openjdk-7-jre
+    apt-get install -y libpq-dev python-dev mysql-client netcat openjdk-8-jre
 
 ARG userid=999
 ARG groupid=999