[MacPorts] #70528: cadabra2 @2.5.4: inaccurate error claiming nlohmann-json is installed

[MacPorts]

#70528: cadabra2 @2.5.4: inaccurate error claiming nlohmann-json is installed
------------------------+----------------------
 Reporter:  ryandesign  |      Owner:  (none)
     Type:  defect      |     Status:  new
 Priority:  Normal      |  Milestone:
Component:  ports       |    Version:  2.10.0
 Keywords:              |       Port:  cadabra2
------------------------+----------------------
 cadabra2 fails to build:

 {{{
 ****
 **** cadabra2 uses its own bundled version of nlohmann/json.hpp
 **** The build will fail if the nlohmann-json port is active.
 **** Please deactivate it:
 ****     sudo port deactivate nlohmann-json
 **** You can reactivate it after installing cadabra2:
 ****     sudo port activate nlohmann-json
 ****

 Error: Failed to configure cadabra2: nlohmann-json installed.
 }}}

 nlohmann-json is ''not'' installed. This occurs on the buildbot workers
 and nlohmann-json is not in cadabra2's recursive dependencies and non-
 dependencies are always deactivated before builds on the buildbot.

 Note that the portfile code only prints this error if
 ${prefix}/include/nlohmann/json.hpp ''does not'' exist, therefore the port
 can currently only be installed if nlohmann-json ''is'' installed and
 trace mode is not used.

 If cadabra2 cannot be built when the nlohmann-json port is installed, the
 conflicts_build portgroup should be used rather than reinventing the wheel
 in the portfile.

-- 
Ticket URL: <https://trac.macports.org/ticket/70528>
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