tweaking settings to be safer, and removing requirement of psycopg2 for django

bin/compile

@@ -45,10 +45,11 @@ if [ "$NAME" = "Python/Django" ]; then
   echo "       Injecting code into $SETTINGS_FILE to read from DATABASE_URL"
   
   cat >>$SETTINGS_FILE <<EOF
-
 import os, urlparse
-if os.environ.has_key('DATABASE_URL'):
+try:
+    if os.environ.has_key('DATABASE_URL'):
         urlparse.uses_netloc.append('postgres')
+        urlparse.uses_netloc.append('mysql')
         url = urlparse.urlparse(os.environ['DATABASE_URL'])
         DATABASES['default'] = {
             'ENGINE':   'django.db.backends.postgresql_psycopg2',
@@ -58,6 +59,14 @@ if os.environ.has_key('DATABASE_URL'):
             'HOST':     url.hostname,
             'PORT':     url.port,
         }
+        if 'postgres' in os.environ['DATABASE_URL']:
+            DATABASES['default']['ENGINE'] = 'django.db.backends.postgresql_psycopg2',
+        if 'mysql' in os.environ['DATABASE_URL']:
+            DATABASES['default']['ENGINE'] = 'django.db.backends.mysql',
+except:
+    print "Unexpected error:", sys.exc_info()
+    raise
+
 EOF
 
   echo "-----> Django script installation"
@@ -75,10 +84,6 @@ PIP_DOWNLOAD_CACHE=$PIP_DOWNLOAD_CACHE bin/pip install -r requirements.txt | sed
 echo "-----> Making virtualenv relocatable"
 virtualenv --relocatable . | sed -u 's/^/       /'
 
-if [ "$NAME" = "Python/Django" ]; then
-  bin/pip freeze | grep psycopg2 > /dev/null || { echo " !     Missing psycopg2 dependency in requirements.txt"; exit 1; }
-fi
-
 # store new artifacts in cache
 for dir in $VIRTUALENV_DIRS; do
   rm -rf $CACHE_DIR/$dir