ubuntu@ip-10-0-0-91:~$ sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following package was automatically installed and is no longer required:
  grub-gfxpayload-lists
Use 'apt-get autoremove' to remove it.
The following packages have been kept back:
  acpid apparmor apt apt-transport-https apt-utils aptitude aptitude-common at
  byobu cloud-init cron curl eatmydata gawk gdisk gir1.2-glib-2.0 gnupg
  iputils-ping isc-dhcp-client isc-dhcp-common libapt-pkg4.12 libcurl3
  libcurl3-gnutls libcwidget3 libept1.4.12 libglib2.0-0 libgnutls-openssl27
  libicu52 libldap-2.4-2 liblog-message-simple-perl libpam-systemd
  libpython-stdlib libpython2.7 libpython2.7-minimal libpython2.7-stdlib
  libstdc++6 libsystemd-daemon0 libxapian22 linux-headers-generic
  linux-headers-virtual linux-image-virtual linux-virtual logrotate lshw
  ntfs-3g parted popularity-contest python python-apt python-minimal
  python-openssl python-pycurl python-requests python-twisted-core
  python-twisted-names python-twisted-web python-urllib3 python-xapian
  python2.7 python2.7-minimal python3-apt python3-gi python3-pycurl rsyslog
  systemd-shim wget
The following packages will be upgraded:
  accountsservice dbus initramfs-tools initscripts libaccountsservice0
  libcryptsetup4 libgcr-base-3-1 libpolkit-backend-1-0 libpolkit-gobject-1-0
  libudev1 open-vm-tools openssh-client openssh-server openssh-sftp-server
  plymouth ppp resolvconf sysv-rc udev unattended-upgrades util-linux
  uuid-runtime
22 upgraded, 0 newly installed, 0 to remove and 66 not upgraded.
Need to get 0 B/5177 kB of archives.
After this operation, 2099 kB of additional disk space will be used.
Do you want to continue? [Y/n]
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
        LANGUAGE = (unset),
        LC_ALL = (unset),
        LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory
Preconfiguring packages ...
(Reading database ... 52312 files and directories currently installed.)
Preparing to unpack .../plymouth_0.9.0-9_amd64.deb ...
Unpacking plymouth (0.9.0-9) over (0.8.8-0ubuntu17.1) ...
dpkg: error processing archive /var/cache/apt/archives/plymouth_0.9.0-9_amd64.deb (--unpack):
 trying to overwrite '/lib/x86_64-linux-gnu/libply-splash-graphics.so.2.1.0', which is also in package libplymouth2:amd64 0.8.8-0ubuntu17.1
Processing triggers for man-db (2.7.0.2-5) ...
Errors were encountered while processing:
 /var/cache/apt/archives/plymouth_0.9.0-9_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
ubuntu@ip-10-0-0-91:~$