migrate apply-config-from-env.py from python2 to python3 (apache#3614)

Fix apache#3549

Descriptions of the changes in this PR:
migrate apply-config-from-env.py from python2 to python3
fix docker/Dockerfile

### Motivation

Issue 3549: migrate apply-config-from-env.py from python2 to python3

### Changes

add newline character, and reformat for docker/Dockerfile
change print to print()

Master Issue: 3549

docker/scripts/apply-config-from-env.py

@@ -29,7 +29,7 @@
 import os, sys
 
 if len(sys.argv) != 2:
-    print 'Usage: %s ' + 'config_dir' % (sys.argv[0])
+    print('Usage: %s ' + 'config_dir' % (sys.argv[0]))
     sys.exit(1)
 
 def mylistdir(dir):
@@ -38,8 +38,8 @@ def mylistdir(dir):
 # Always apply env config to all the files under conf
 conf_dir = sys.argv[1]
 conf_files = mylistdir(conf_dir)
-print 'conf files: '
-print conf_files
+print('conf files: ')
+print(conf_files)
 
 bk_env_prefix = 'BK_'
 zk_env_prefix = 'ZK_'
@@ -75,13 +75,13 @@ def mylistdir(dir):
         if k.startswith(bk_env_prefix):
             search_key = k[len(bk_env_prefix):]
             if search_key in keys:
-                print '[%s] Applying config %s = %s' % (conf_filename, search_key, v)
+                print('[%s] Applying config %s = %s' % (conf_filename, search_key, v))
                 idx = keys[search_key]
                 lines[idx] = '%s=%s\n' % (search_key, v)
         if k.startswith(zk_env_prefix):
             search_key = k[len(zk_env_prefix):]
             if search_key in keys:
-                print '[%s] Applying config %s = %s' % (conf_filename, search_key, v)
+                print('[%s] Applying config %s = %s' % (conf_filename, search_key, v))
                 idx = keys[search_key]
                 lines[idx] = '%s=%s\n' % (search_key, v)