[tex-live] Texlive update failed with signature error

[FX]

Find below the information requested.
curl is macOS 10.13.4 system curl.

$ curl -V
curl 7.54.0 (x86_64-apple-darwin17.0) libcurl/7.54.0 LibreSSL/2.0.20 zlib/1.2.11 nghttp2/1.24.0
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtsp smb smbs smtp smtps telnet tftp 
Features: AsynchDNS IPv6 Largefile GSS-API Kerberos SPNEGO NTLM NTLM_WB SSL libz HTTP2 UnixSockets HTTPS-proxy 

$ sudo tlmgr -v update --repository http://ctan.crest.fr/tex-archive/systems/texlive/tlnet --list
D:tlmgr:main: ::tldownload_server defined: TeXLive::TLDownload=HASH(0x7fb4d10d1b98)
D:Using system curl (tested).
D:Using shipped /usr/local/texlive/2018/tlpkg/installer/wget/wget.x86_64-darwin for wget (tested).
D:Using shipped /usr/local/texlive/2018/tlpkg/installer/lz4/lz4.x86_64-darwin for lz4 (tested).
D:Using system gzip (tested).
D:Using shipped /usr/local/texlive/2018/tlpkg/installer/xz/xz.x86_64-darwin for xz (tested).
D:Using checksum method digest::sha
D:Testing for gpg in gpg
D: ... gpg not ok! [gpg --version >/dev/null 2>&1]
D:Testing for gpg in gpg2
D: ... gpg not ok! [gpg2 --version >/dev/null 2>&1]
D:Testing for gpg in /usr/local/texlive/2018/tlpkg/installer/gpg/gpg.x86_64-darwin
D:gpg command line: "/usr/local/texlive/2018/tlpkg/installer/gpg/gpg.x86_64-darwin" --homedir "/usr/local/texlive/2018/tlpkg/gpg" --no-secmem-warning --no-permission-warning --lock-never 
D:will verify cryptographic signatures
D:TLPDB.pm: trying to initialize from http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb
D:trying to download http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.xz to /tmp/N5M2fXFn45/kanxa6Z72O
D:persistent connection set up, trying to get http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.xz (for /tmp/N5M2fXFn45/kanxa6Z72O)
D:TLDownload::get_file: response error: 500 Can't verify SSL peers without knowing which Certificate Authorities to trust (for http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.xz)
D:TLUtils::download_file: persistent connection ok, but download failed: http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.xz
D:TLUtils::download_file: retrying with wget.
D:TLUtils::_download_file_program: curl http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.xz /tmp/N5M2fXFn45/kanxa6Z72O
D:downloading http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.xz using curl --user-agent texlive/curl --retry 10 --connect-timeout 30 --silent --output
D:download of http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.xz succeeded
D:TLUtils::download_file: downloading using curl succeeded
D:decompressing /tmp/N5M2fXFn45/kanxa6Z72O to /tmp/N5M2fXFn45/4z3B8K540K
D:found the uncompressed xz file
D:persistent connection set up, trying to get http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512 (for /tmp/N5M2fXFn45/RfbdfXZZ7u)
D:TLDownload::get_file: response error: 500 Can't verify SSL peers without knowing which Certificate Authorities to trust (for http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512)
D:TLUtils::download_file: persistent connection ok, but download failed: http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512
D:TLUtils::download_file: retrying with wget.
D:TLUtils::_download_file_program: curl http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512 /tmp/N5M2fXFn45/RfbdfXZZ7u
D:downloading http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512 using curl --user-agent texlive/curl --retry 10 --connect-timeout 30 --silent --output
D:download of http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512 succeeded
D:TLUtils::download_file: downloading using curl succeeded
D:persistent connection set up, trying to get http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512.asc (for /tmp/N5M2fXFn45/2bOqdPZaKV)
D:TLDownload::get_file: response error: 500 Can't verify SSL peers without knowing which Certificate Authorities to trust (for http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512.asc)
D:TLUtils::download_file: persistent connection ok, but download failed: http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512.asc
D:TLUtils::download_file: retrying with wget.
D:TLUtils::_download_file_program: curl http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512.asc /tmp/N5M2fXFn45/2bOqdPZaKV
D:downloading http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512.asc using curl --user-agent texlive/curl --retry 10 --connect-timeout 30 --silent --output
D:download of http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512.asc succeeded
D:TLUtils::download_file: downloading using curl succeeded
D:verify_checksum: returning 2 and cryptographic signature verification of
  /tmp/N5M2fXFn45/RfbdfXZZ7u
against
  http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512.asc
failed. Output was
gpg: no valid OpenPGP data found.
gpg: the signature could not be verified.
Please remember that the signature file (.sig or .asc)
should be the first file given on the command line.

Please report to texlive at tug.org

/Library/TeX/texbin/tlmgr: signature verification error of /tmp/N5M2fXFn45/4z3B8K540K from http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb: cryptographic signature verification of
  /tmp/N5M2fXFn45/RfbdfXZZ7u
against
  http://ctan.crest.fr/tex-archive/systems/texlive/tlnet/tlpkg/texlive.tlpdb.sha512.asc
failed. Output was
gpg: no valid OpenPGP data found.
gpg: the signature could not be verified.
Please remember that the signature file (.sig or .asc)
should be the first file given on the command line.

Please report to texlive at tug.org