Error target not found arch

Several times I updated pacman -Syy , pacman -Syu and some other commands.
I have multilib source uncommented in pacman.conf.
My last thoughts were about pacman-key, I was trying to change keyserver in /etc/pacman.d/gnupg/gnu.conf, run pacman-key --refresh-keys and pacman-key --populate archlinux but it didn’t help me. Was googling a lot, but I guess I need to ask here.
pacman -S xorg works, but pacman -S yaourt and several others not

UPD: pacman.conf

 #
# /etc/pacman.conf
#
# See the pacman.conf(5) manpage for option and repository directives

#
# GENERAL OPTIONS
#
[options]
# The following paths are commented out with their default values listed.
# If you wish to use different paths, uncomment and update the paths.
#RootDir     = /
#DBPath      = /var/lib/pacman/
#CacheDir    = /var/cache/pacman/pkg/
#LogFile     = /var/log/pacman.log
#GPGDir      = /etc/pacman.d/gnupg/
#HookDir     = /etc/pacman.d/hooks/
HoldPkg     = pacman glibc
#XferCommand = /usr/bin/curl -C - -f %u > %o
#XferCommand = /usr/bin/wget --passive-ftp -c -O %o %u
#CleanMethod = KeepInstalled
#UseDelta    = 0.7
Architecture = auto

# Pacman won't upgrade packages listed in IgnorePkg and members of IgnoreGroup
#IgnorePkg   =
#IgnoreGroup =

#NoUpgrade   =
#NoExtract   =

# Misc options
#UseSyslog
#Color
#TotalDownload
CheckSpace
#VerbosePkgLists

# By default, pacman accepts packages signed by keys that its local keyring
# trusts (see pacman-key and its man page), as well as unsigned packages.
SigLevel    = Never
LocalFileSigLevel = Optional
#RemoteFileSigLevel = Required

# NOTE: You must run `pacman-key --init` before first using pacman; the local
# keyring can then be populated with the keys of all official Arch Linux
# packagers with `pacman-key --populate archlinux`.

#
# REPOSITORIES
#   - can be defined here or included from another file
#   - pacman will search repositories in the order defined here
#   - local/custom mirrors can be added here or in separate files
#   - repositories listed first will take precedence when packages
#     have identical names, regardless of version number
#   - URLs will have $repo replaced by the name of the current repo
#   - URLs will have $arch replaced by the name of the architecture
#
# Repository entries are of the format:
#       [repo-name]
#       Server = ServerName
#       Include = IncludePath
#
# The header [repo-name] is crucial - it must be present and
# uncommented to enable the repo.
#

# The testing repositories are disabled by default. To enable, uncomment the
# repo name header and Include lines. You can add preferred servers immediately
# after the header, and they will be used before the default mirrors.

#[testing]
#Include = /etc/pacman.d/mirrorlist

[core]
Include = /etc/pacman.d/mirrorlist

[extra]
Include = /etc/pacman.d/mirrorlist

#[community-testing]
#Include = /etc/pacman.d/mirrorlist

[community]
Include = /etc/pacman.d/mirrorlist

# If you want to run 32 bit applications on your x86_64 system,
# enable the multilib repositories as required here.

#[multilib-testing]
#Include = /etc/pacman.d/mirrorlist

[multilib]
Include = /etc/pacman.d/mirrorlist

# An example of a custom package repository.  See the pacman manpage for
# tips on creating your own repositories.
#[custom]
#SigLevel = Optional TrustAll
#Server = file:///home/custompkgs

Trying to install

 sudo pacman -S light 
 error: target not found: light 
 sudo pacman -S alsamixer
 error: target not found: alsamixer   

The other day I tried to install a package from AUR using Yay helper program. The package I tried to install has many Python dependencies. Unfortunately, I couldn’t install it and Yay kept throwing the following error. I thought the problem would be solved if I remove the conflicting packages. But, I don’t want to break the system. Here is the output error message when I tried to install a program from AUR:

 error: failed to commit transaction (conflicting files)
 python-tabulate: /usr/bin/tabulate exists in filesystem
 python-tabulate: /usr/lib/python3.6/site-packages/__pycache__/tabulate.cpython-36.pyc exists in filesystem
 python-tabulate: /usr/lib/python3.6/site-packages/tabulate.py exists in filesystem
 Errors occurred, no packages were upgraded.
 :: Building torrench package(s)...
 ==> Making package: torrench 1.0.56-1 (Mon Oct 23 15:46:37 IST 2017)
 ==> Checking runtime dependencies...
 ==> Installing missing dependencies...
 error: target not found: python-tabulate
 ==> ERROR: 'pacman' failed to install missing dependencies.

As you can see in the above output, the following three packages were the ones that causing the problem.

1. /usr/bin/tabulate
2. /usr/lib/python3.6/site-packages/__pycache__/tabulate.cpython-36.pyc
3. /usr/lib/python3.6/site-packages/tabulate.py

Solve «ERROR: ‘pacman’ failed to install missing dependencies» In Arch Linux

To me, deleting the problematic packages fixed the problem. However, it is always recommend to check the problematic files are not owned by some other packages. Because If it is owned by some other program, deleting them is bad idea. So, you need to find those conflicting files are not owned by any other packages. The pacman command can easily find out if a file is owned by other packages in your Arch Linux system.

In my case, I checked whether the above mentioned files are owned some other packages as shown below.

$ sudo pacman -Qo /usr/bin/tabulate

Sample output:

error: No package owns /usr/bin/tabulate

$ sudo pacman -Qo /usr/lib/python3.6/site-packages/__pycache__/tabulate.cpython-36.pyc

Sample output:

error: No package owns /usr/lib/python3.6/site-packages/__pycache__/tabulate.cpython-36.pyc

$ sudo pacman -Qo /usr/lib/python3.6/site-packages/tabulate.py

Sample output:

error: No package owns /usr/lib/python3.6/site-packages/tabulate.py

As you can see, all of the above commands showed me that those files are not owned by any packages. So, I simply deleted them one by one.

$ sudo rm /usr/bin/tabulate

$ sudo rm /usr/lib/python3.6/site-packages/__pycache__/tabulate.cpython-36.pyc

$ sudo rm /usr/lib/python3.6/site-packages/tabulate.py

Done! Now, I can be able to install all packages with Python dependencies. For safety a precaution, backup those conflicting files before deleting them. You can restore them just in case if there are any problems after deleting them.