brew doctor Warning: Calling 'depends_on :python3' is deprecated!

Warning- Calling 'depends_on -python3' is deprecated!.txt

Hi - For the past few days, 'brew doctor' and 'brew services list' have been coughing up
warnings that 'brew upgrade/update' seem not to have fixed:

==> Warning: Calling 'depends_on :python3' is deprecated!
    Use 'depends_on "python3"' instead.
    
Warnings from 'brew upgrade/update' & 'brew services list' point to two locations,

/usr/local/Homebrew/Library/Homebrew/dependency_collector.rb:88:in `parse_spec'
and
/usr/local/Homebrew/Library/Taps/homebrew/homebrew-services/cmd/brew-services.rb:86:in `available_services'

but I don't find a reference to 'depends_on :python3' in either file.
This doesn't seem to have affected subsequent builds or upgrades on my system,
but I wonder if the warning can be safely ignored, or better, addressed and removed?
I see the warning in the gist-logs for python3:

➜  ~ brew gist-logs python3
https://gist.github.com/21c6e788f4e7b82e61f0e498593cf562
➜  ~

Here is what I am seeing on my system:

Last login: Mon Jan 22 13:08:03 on ttys001
➜  ~ brew update
Already up-to-date.
➜  ~ brew update
Already up-to-date.
➜  ~ brew doctor
Warning: Calling 'depends_on :python3' is deprecated!
Use 'depends_on "python3"' instead.
/usr/local/Homebrew/Library/Homebrew/dependency_collector.rb:88:in `parse_spec'

Your system is ready to brew.
➜  ~ brew services list
Warning: Calling 'depends_on :python3' is deprecated!
Use 'depends_on "python3"' instead.
/usr/local/Homebrew/Library/Taps/homebrew/homebrew-services/cmd/brew-services.rb:86:in `available_services'
Please report this to the homebrew/services tap!

Name    Status  User     Plist
couchdb started cwalston /Users/cwalston/Library/LaunchAgents/homebrew.mxcl.couchdb.plist
jack    stopped
➜  ~ brew config
HOMEBREW_VERSION: 1.5.1
ORIGIN: https://github.com/Homebrew/brew.git
HEAD: ace2d569dcd3a45d0fc49a6742540b6f7a957fbc
Last commit: 12 hours ago
Core tap ORIGIN: https://github.com/Homebrew/homebrew-core
Core tap HEAD: 0de24ffa7c2c844a3c0b1db26e0e7e46229ac180
Core tap last commit: 35 minutes ago
HOMEBREW_PREFIX: /usr/local
HOMEBREW_DEV_CMD_RUN: 1
CPU: quad-core 64-bit broadwell
Homebrew Ruby: 2.3.3 => /usr/local/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.3/bin/ruby
Clang: 8.0 build 800
Git: 2.16.1 => /usr/local/bin/git
Curl: 7.43.0 => /usr/bin/curl
Perl: /usr/local/bin/perl => /usr/local/Cellar/perl/5.26.1/bin/perl
Python: /usr/local/opt/python/libexec/bin/python => /usr/local/Cellar/python/2.7.14_2/Frameworks/Python.framework/Versions/2.7/bin/python2.7
Ruby: /usr/local/bin/ruby => /usr/local/Cellar/ruby/2.5.0/bin/ruby
Java: 1.6.0_65-b14-468
macOS: 10.11.6-x86_64
Xcode: 8.2.1
CLT: 8.2.0.0.1.1480973914
X11: 2.7.11 => /opt/X11
➜  ~