Seems it is because fail to download this url:
http://maven.twttr.com/org/apache/apache/14/apache-14.pom


------------------ 原始邮件 ------------------
发件人: "Ted Yu";<yuzhihong@gmail.com>;
发送时间: 2016年5月1日(星期天) 晚上9:27
收件人: "sunday2000"<2314476218@qq.com>;
抄送: "user"<user@spark.apache.org>;
主题: Re: Why Non-resolvable parent POM for org.apache.spark:spark-parent_2.10:1.6.1:Could not transfer artifact org.apache:apache:pom:14 from/to central(https://repo1.maven.org/maven2): repo1.maven.org: unknown error

bq. Non-resolvable parent POM for org.apache.spark:spark-parent_2.10:1.6.1

Looks like you were using Spark 1.6.1

Can you check firewall settings ?

I saw similar report from Chinese users.

Consider using proxy.

On Sun, May 1, 2016 at 4:19 AM, sunday2000 <2314476218@qq.com> wrote:
Hi,
  We are compiling spare 1.6.0 in a linux server, while getting this error message. Could you tell us how to solve it? thanks.

[INFO] Scanning for projects...
[ERROR] [ERROR] Some problems were encountered while processing the POMs:
[FATAL] Non-resolvable parent POM for org.apache.spark:spark-parent_2.10:1.6.1: Could not transfer artifact org.apache:apache:pom:14 from/to central (https://repo1.maven.org/maven2): repo1.maven.org: unknown error and 'parent.relativePath' points at wrong local POM @ line 22, column 11
 @ 
[ERROR] The build could not read 1 project -> [Help 1]
[ERROR]   
[ERROR]   The project org.apache.spark:spark-parent_2.10:1.6.1 (/data/spark/spark-1.6.1/pom.xml) has 1 error
[ERROR]     Non-resolvable parent POM for org.apache.spark:spark-parent_2.10:1.6.1: Could not transfer artifact org.apache:apache:pom:14 from/to central (https://repo1.maven.org/maven2): repo1.maven.org: unknown error and 'parent.relativePath' points at wrong local POM @ line 22, column 11: Unknown host repo1.maven.org: unknown error -> [Help 2]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles: