"Resources are low on NN" after deactivation of safemode and added space - hadoop

Question

I'm trying mapreduce with python in accord with http://www.michael-noll.com/tutorials/writing-an-hadoop-mapreduce-program-in-python/
I've received a "Resources are low on NN" continously when I'm trying my mapreduce job in hadoop. I've removed files from hdfs and also attached a volume to the instance on the cloud. I've deactivated safemode but the problem is that it activates instantly again.
Filesystem Size Used Available Use%
hdfs://localhost:9000 38.8 G 9.3 G 26.4 G 24%
I should have enough space...
The python files has been tested locally and works fine. In fact, this has worked on the cloud before but for some reason it doesn't anymore.
ubuntu#lesolab2:~$ hadoop jar /usr/local/hadoop/share/hadoop/tools/lib/hadoop-streaming-2.7.2.jar -file mapper.py -mapper mapper.py -file reducer.py -reducer reducer.py -input /user/python/tweets/files/* -output /user/python/result
16/04/25 14:22:09 WARN streaming.StreamJob: -file option is deprecated, please use generic option -files instead.
packageJobJar: [mapper.py, reducer.py] [] /tmp/streamjob5539719163695874514.jar tmpDir=null
16/04/25 14:22:10 INFO Configuration.deprecation: session.id is deprecated. Instead, use dfs.metrics.session-id
16/04/25 14:22:10 INFO jvm.JvmMetrics: Initializing JVM Metrics with processName=JobTracker, sessionId=
16/04/25 14:22:10 INFO jvm.JvmMetrics: Cannot initialize JVM Metrics with processName=JobTracker, sessionId= - already initialized
16/04/25 14:22:11 INFO mapred.FileInputFormat: Total input paths to process : 21
16/04/25 14:22:11 INFO net.NetworkTopology: Adding a new node: /default-rack/127.0.0.1:50010
16/04/25 14:22:11 INFO mapreduce.JobSubmitter: number of splits:86
16/04/25 14:22:11 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_local1741181014_0001
16/04/25 14:22:12 INFO mapred.LocalDistributedCacheManager: Localized file:/home/ubuntu/mapper.py as file:/tmp/hadoop-ubuntu/mapred/local/1461594132014/mapper.py
16/04/25 14:22:12 INFO mapred.LocalDistributedCacheManager: Localized file:/home/ubuntu/reducer.py as file:/tmp/hadoop-ubuntu/mapred/local/1461594132015/reducer.py
16/04/25 14:22:12 INFO mapreduce.Job: The url to track the job: http://localhost:8080/
16/04/25 14:22:12 INFO mapreduce.Job: Running job: job_local1741181014_0001
16/04/25 14:22:12 INFO mapred.LocalJobRunner: OutputCommitter set in config null
16/04/25 14:22:12 INFO mapred.LocalJobRunner: OutputCommitter is org.apache.hadoop.mapred.FileOutputCommitter
16/04/25 14:22:12 INFO output.FileOutputCommitter: File Output Committer Algorithm version is 1
16/04/25 14:22:12 INFO mapred.LocalJobRunner: Error cleaning up job:job_local1741181014_0001
16/04/25 14:22:12 WARN mapred.LocalJobRunner: job_local1741181014_0001
org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.server.namenode.SafeModeException): Cannot create directory /user/python/result/_temporary/0. Name node is in safe mode.
Resources are low on NN. Please add or free up more resources then turn off safe mode manually. NOTE: If you turn off safe mode before adding resources, the NN will immediately return to safe mode. Use "hdfs dfsadmin -safemode leave" to turn safe mode off.
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkNameNodeSafeMode(FSNamesystem.java:1327)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirs(FSNamesystem.java:3893)
at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.mkdirs(NameNodeRpcServer.java:983)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.mkdirs(ClientNamenodeProtocolServerSideTranslatorPB.java:622)
at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:616)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:969)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2049)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2045)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2043)
at org.apache.hadoop.ipc.Client.call(Client.java:1475)
at org.apache.hadoop.ipc.Client.call(Client.java:1412)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:229)
at com.sun.proxy.$Proxy9.mkdirs(Unknown Source)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.mkdirs(ClientNamenodeProtocolTranslatorPB.java:558)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:191)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
at com.sun.proxy.$Proxy10.mkdirs(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient.primitiveMkdir(DFSClient.java:3000)
at org.apache.hadoop.hdfs.DFSClient.mkdirs(DFSClient.java:2970)
at org.apache.hadoop.hdfs.DistributedFileSystem$21.doCall(DistributedFileSystem.java:1047)
at org.apache.hadoop.hdfs.DistributedFileSystem$21.doCall(DistributedFileSystem.java:1043)
at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
at org.apache.hadoop.hdfs.DistributedFileSystem.mkdirsInternal(DistributedFileSystem.java:1043)
at org.apache.hadoop.hdfs.DistributedFileSystem.mkdirs(DistributedFileSystem.java:1036)
at org.apache.hadoop.fs.FileSystem.mkdirs(FileSystem.java:1877)
at org.apache.hadoop.mapreduce.lib.output.FileOutputCommitter.setupJob(FileOutputCommitter.java:305)
at org.apache.hadoop.mapred.FileOutputCommitter.setupJob(FileOutputCommitter.java:131)
at org.apache.hadoop.mapred.OutputCommitter.setupJob(OutputCommitter.java:233)
at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:511)
16/04/25 14:22:13 INFO mapreduce.Job: Job job_local1741181014_0001 running in uber mode : false
16/04/25 14:22:13 INFO mapreduce.Job: map 0% reduce 0%
16/04/25 14:22:13 INFO mapreduce.Job: Job job_local1741181014_0001 failed with state FAILED due to: NA
16/04/25 14:22:13 INFO mapreduce.Job: Counters: 0
16/04/25 14:22:13 ERROR streaming.StreamJob: Job not successful!
Streaming Command Failed!
Any ideas to why the streaming fails?