HDF5 formula no longer supports mpich

[greenc-FNAL]

• are reporting a bug others will be able to reproduce and not asking a question. If you're not sure or want to ask a question do so on our Discourse: https://discourse.brew.sh
• have a problem with brew install (or upgrade, reinstall) a single, official formula (not cask)? If it's a general brew problem please file this issue at Homebrew/brew: https://github.com/Homebrew/brew/issues/new. If it's a brew cask problem please file this issue at https://github.com/caskroom/homebrew-cask/issues/new. If it's a tap (e.g. Homebrew/homebrew-php) problem please file this issue at the tap.
• ran brew update and can still reproduce the problem?
• ran brew doctor, fixed all issues and can still reproduce the problem?
  Remaining issues (see below) are irrelevant to the problem at hand.
• ran brew gist-logs <formula> (where <formula> is the name of the formula that failed) and included the output link?

   Error: No logs.

• if brew gist-logs didn't work: ran brew config and brew doctor and included their output with your issue?

To help us debug your issue please explain:

• What you were trying to do (and why)

   brew update && brew outdated && brew upgrade && brew cleanup

• What happened (include command output)

   ==> Upgrading hdf5 --with-mpi
   Error: /usr/local/opt/open-mpi not present or broken
   Please reinstall open-mpi. Sorry :(

• What you expected to happen
  Successful upgrade.
• Step-by-step reproduction instructions (by running brew install commands)
  Either (to duplicate what actually happened):
• Check out homebrew core prior to dc5b5d699b
• brew install mpich
• brew install hdf5 --with-mpi
• Update to HEAD.
• brew upgrade
  Or (to produce the same error with less effort):
• brew install mpich
• brew install hdf5 --with-mpi

I understand that this is probably intentional. However: there are multiple MPI implementations for a reason, and people choose to use implementations other than open-mpi for perfectly valid reasons. For us, for example, open-mpi exhibited problems under certain conditions, whereas mpich did not.

Please, is there any documentation or discussion explaining why the :mpi dependency is being phased out? This has removed functionality upon which we depend, and has rendered Homebrew less useful to us, which is why I report this as a bug.

[greenc-FNAL]

• Output of brew config:

HOMEBREW_VERSION: 1.6.1-41-g648a7c7
ORIGIN: https://github.com/Homebrew/brew
HEAD: 648a7c7b1ed540e0629d3ce0a8b68a4a3dc9faed
Last commit: 21 hours ago
Core tap ORIGIN: https://github.com/Homebrew/homebrew-core
Core tap HEAD: 22511f2e939b274a4e0818d82885522279adf654
Core tap last commit: 2 hours ago
HOMEBREW_PREFIX: /usr/local
HOMEBREW_DEV_CMD_RUN: 1
HOMEBREW_VISUAL: edit
CPU: octa-core 64-bit skylake
Homebrew Ruby: 2.3.3 => /usr/local/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.3/bin/ruby
Clang: 9.1 build 902
Git: 2.17.0 => /usr/local/bin/git
Curl: 7.54.0 => /usr/bin/curl
Java: 9.0.4, 1.8.0_162
macOS: 10.13.4-x86_64
CLT: 9.3.0.0.1.1521514116
Xcode: 9.3
XQuartz: 2.7.11 => /opt/X11

• Output of brew doctor.

Please note that these warnings are just used to help the Homebrew maintainers
with debugging if you file an issue. If everything you use Homebrew for is
working fine: please don't worry or file an issue; just ignore this. Thanks!

Warning: Unbrewed dylibs were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected dylibs:
  /usr/local/lib/libtcl8.6.dylib
  /usr/local/lib/libtk8.6.dylib

Warning: Unbrewed header files were found in /usr/local/include.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected header files:
  /usr/local/include/fakemysql.h
  /usr/local/include/fakepq.h
  /usr/local/include/fakesql.h
  /usr/local/include/itcl.h
  /usr/local/include/itcl2TclOO.h
  /usr/local/include/itclDecls.h
  /usr/local/include/itclInt.h
  /usr/local/include/itclIntDecls.h
  /usr/local/include/itclMigrate2TclCore.h
  /usr/local/include/itclTclIntStubsFcn.h
  /usr/local/include/mysqlStubs.h
  /usr/local/include/odbcStubs.h
  /usr/local/include/pqStubs.h
  /usr/local/include/tcl.h
  /usr/local/include/tclDecls.h
  /usr/local/include/tclOO.h
  /usr/local/include/tclOODecls.h
  /usr/local/include/tclPlatDecls.h
  /usr/local/include/tclThread.h
  /usr/local/include/tclTomMath.h
  /usr/local/include/tclTomMathDecls.h
  /usr/local/include/tdbc.h
  /usr/local/include/tdbcDecls.h
  /usr/local/include/tdbcInt.h
  /usr/local/include/tk.h
  /usr/local/include/tkDecls.h
  /usr/local/include/tkPlatDecls.h

Warning: Unbrewed .pc files were found in /usr/local/lib/pkgconfig.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected .pc files:
  /usr/local/lib/pkgconfig/tcl.pc
  /usr/local/lib/pkgconfig/tk.pc

Warning: Unbrewed static libraries were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected static libraries:
  /usr/local/lib/libtclstub8.6.a
  /usr/local/lib/libtkstub8.6.a

[fxcoudert]

In January, we phased out generic support for MPI. MPI support for core formulas now requires OpenMPI as reference implementation: #22703 #22820