It is not a bug

PPA: NO_PUBKEY C2518248EEA14886

I faced the following error in Ubuntu 15.04 when trying to: sudo apt-get update

GPG error: http://ppa.launchpad.net vivid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C2518248EEA14886

Googling, there are several solutions for it, but none worked.
Only a old script that is in a couple of Ubuntu forums:

http://ubuntuforums.org/archive/index.php/t-2257304.html





Script:

#!/bin/sh
# This script adds PPA keys to the primary keyring in /etc/apt/trusted.gpg
# thus getting around the GPG limit of 40 keyrings.
# WARNING: It's only intended as the last resort measure.
# Rather than using it, reduce your use of PPAs.
set -e

keyserver=http://keyserver.ubuntu.com:11371
launchpadapi=https://launchpad.net/api/1.0

[ -r /etc/lsb-release ] && . /etc/lsb-release ||
{ echo Cannot read /etc/lsb-release >&2; exit 1;}

[ Ubuntu = "$DISTRIB_ID" ] ||
{ echo This script is supposed to run on Ubuntu >&2; exit 2;}

[ -n "$DISTRIB_CODENAME" ] && codename=$DISTRIB_CODENAME ||
{ echo Cannot determine installed Ubuntu release >&2; exit 2;}
release=$DISTRIB_RELEASE

usage() {
# Parameter: $1 - error message
<<! cat >&2
$1
Usage: sudo $0
Example: sudo $0 $codename
!
exit 3
}

[ 0 = `id -u` ] || usage "Please run with sudo"



if [ -x /usr/bin/ubuntu-distro-info ]
then
codenames=`/usr/bin/ubuntu-distro-info --all | tr '\n' \|`
eval \
case \$1 in \
"$codenames$codename"') codename=$1;;
*) usage "Wrong release name: $1";;' \
esac
else
[ 12 -le "${release%%.*}" ] &&
<<! cat >&2
This script works best with package 'distro-info' installed.

Consider installing distro-info with
sudo apt-get install distro-info

Continuing execution anyway

!

case $1 in
lucid|precise|trusty|utopic|vivid|$codename) codename=$1;;
*) usage "Wrong release name: $1";;
esac
fi

echo "Release: $codename"
echo Please wait...

tempfile() {
# Parameters: $1 - variable to hold the file name
# $2 - short file content description
local tmp
if tmp=`mktemp`
then
eval "$1='$tmp'"
currenttrap="${currenttrap}rm -f -- '$tmp';"
trap "$currenttrap" EXIT
else
echo "Cannot create temporary file for $2" >&2
exit 2
fi
}

tempfile sources 'APT sources'
tempfile fingerprints 'key fingerprints'
tempfile key 'signing key'

sourcelist=/etc/apt/sources.list
eval $(apt-config shell sourcelist Dir::Etc::SourceList/f)
sourceparts=/etc/apt/sources.list.d/
eval $(apt-config shell sourceparts Dir::Etc::SourceParts/d)
grep -hs '^[^#]' "$sourcelist" "$sourceparts"*.list > "$sources" ||:
grep -q '^Types:' "$sources" && {
echo "This script doesn't work with RFC822-style sources.list" >&2; exit 2
}

for ppaowner in $(
awk -F/ '/^deb[ \t]+.*ppa\.launchpad.*[ \t]+'$codename'/{print$4}' \
"$sources"
)
do
wget -qO- "$launchpadapi/~$ppaowner/ppas" |
awk -F'": "|"}' -v'RS="?, "' '/key_fingerprint/{print $2}' |
sort -u >> "$fingerprints"
done
for fingerprint in `sort -u "$fingerprints"`
do
wget -qO- "$keyserver/pks/lookup?op=get&search=0x$fingerprint" |
sed '/-BEGIN/,/-END/!d' > "$key"
if test "$fingerprint" = "$(
apt-key adv --with-colons --with-fingerprint "$key" |
awk -F: '/^fpr/{print $10}'
)"
then
apt-key add "$key"
else
<<! cat - "$key" >&2
Key rejected: retrieved key doesn't match the fingerprint!

Fingerprint: $fingerprint

Retrieved key:
$(apt-key adv --with-fingerprint "$key")
================================================== ========
!
fi
done

rm -f -- "$sources" "$fingerprints" "$key"
trap - EXIT

WebLogic Server XML Parsers

Many times there are question in WebLogic Server about parser factories:

java.lang.AbstractMethodError: javax.xml.parsers.DocumentBuilderFactory.setFeature

  java.lang.ClassCastException: weblogic.xml.jaxp.RegistryXMLInputFactory cannot be cast to javax.xml.stream.XMLInputFactory
    Error weblogic.xml.jaxp.RegistryXMLInputFactory cannot be cast to javax.xml.stream.XMLInputFactory

 java.lang.NoSuchMethodError: javax.xml.parsers.DocumentBuilderFactory.newInstance(Ljava/lang/String;Ljava/lang/ClassLoader;)Ljavax/xml/parsers/DocumentBuilderFactory;

java.lang.NoClassDefFoundError: org/apache/xerces/jaxp/datatype/XMLGregorianCalendarImpl$Parser




Because the classpath retrieve from different parts these implementations, including the JDK6 which bundles in it now.

This is how you can change by system properties the implementation, using xerces:

-Djavax.xml.parsers.SAXParserFactory=org.apache.xerces.jaxp.SAXParserFactoryImpl -Djavax.xml.parsers.DocumentBuilderFactory=org.apache.xerces.jaxp.DocumentBuilderFactoryImpl -Djavax.xml.parsers.SAXParser=org.apache.xerces.jaxp.SAXParserImpl

maybe you'll need to add xercesImpl.jar to your classpath. 


More info: 
https://docs.oracle.com/cd/E57014_01/wls/WLACH/pagehelp/Corexmlregistryxmlregistryconfigtitle.html