treat colon as special path in modextrapath

[smoors]

needed for fixing easybuilders/easybuild-easyconfigs#19505

draft: not yet working for tcl modules, see comments below

[boegelbot]

@smoors: Tests failed in GitHub Actions, see https://github.com/easybuilders/easybuild-framework/actions/runs/7575661081
Output from first failing test suite run:

ERROR: test_make_module_step (test.framework.easyblock.EasyBlockTest)
Test the make_module_step
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/test/framework/easyblock.py", line 1321, in test_make_module_step
    self.modtool.load(['pi/3.14'])
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/easybuild/tools/modules.py", line 694, in load
    self.run_module('load', mod)
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/easybuild/tools/modules.py", line 1284, in run_module
    return super(EnvironmentModulesTcl, self).run_module(*args, **kwargs)
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/easybuild/tools/modules.py", line 1216, in run_module
    return super(EnvironmentModulesC, self).run_module(*args, **kwargs)
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/easybuild/tools/modules.py", line 842, in run_module
    self.check_module_output(full_cmd, stdout, stderr)
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/easybuild/tools/modules.py", line 1384, in check_module_output
    raise EasyBuildError("Failed module command detected: %s (stdout: %s, stderr: %s)", cmd, stdout, stderr)
easybuild.tools.build_log.EasyBuildError: "Failed module command detected: tclsh /home/runner/libexec/modulecmd.tcl python load pi/3.14 (stdout: _mlstatus = False\n, stderr: Module ERROR: add-path cannot handle path equals to separator string\n  In '/tmp/eb-qmzk51pw/eb-quvkthfz/eb-8m50v45w/tmpgzk_tu2n/modules/all/pi/3.14'\n  Please contact <root@localhost>\n)"

======================================================================
ERROR: test_toy_module_fulltxt (test.framework.toy_build.ToyBuildTest)
Strict text comparison of generated module file.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/test/framework/toy_build.py", line 1452, in test_toy_module_fulltxt
    self.test_toy_tweaked()
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/test/framework/toy_build.py", line 311, in test_toy_tweaked
    outtxt = self.eb_main(args, do_build=True, verbose=True, raise_error=True)
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/test/framework/utilities.py", line 341, in eb_main
    raise myerr
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/test/framework/utilities.py", line 314, in eb_main
    main(args=main_args, logfile=logfile, do_build=do_build, testing=testing, modtool=modtool)
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/easybuild/main.py", line 732, in main
    hooks, do_build)
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/easybuild/main.py", line 566, in process_eb_args
    exit_on_failure=exit_on_failure)
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/easybuild/main.py", line 176, in build_and_install_software
    raise EasyBuildError(test_msg)
easybuild.tools.build_log.EasyBuildError: 'Build of /tmp/eb-qmzk51pw/eb-quvkthfz/eb-6hi2w9dq/tmpcp3yq_iw/toy-0.0-tweaked.eb failed (err: "build failed (first 300 chars): Failed module command detected: tclsh /home/runner/libexec/modulecmd.tcl python load toy/0.0-tweaked (stdout: _mlstatus = False\\n, stderr: Module ERROR: add-path cannot handle path equals to separator string\\n  In \'/tmp/eb-qmzk51pw/eb-quvkthfz/eb-6hi2w9dq/eb-hfqsof5c/eb-ndhqu1x_/tmpfnqoeu71/all/toy/0.")'

======================================================================
ERROR: test_toy_tweaked (test.framework.toy_build.ToyBuildTest)
Test toy build with tweaked easyconfig, for testing extra easyconfig parameters.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/test/framework/toy_build.py", line 311, in test_toy_tweaked
    outtxt = self.eb_main(args, do_build=True, verbose=True, raise_error=True)
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/test/framework/utilities.py", line 341, in eb_main
    raise myerr
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/test/framework/utilities.py", line 314, in eb_main
    main(args=main_args, logfile=logfile, do_build=do_build, testing=testing, modtool=modtool)
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/easybuild/main.py", line 732, in main
    hooks, do_build)
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/easybuild/main.py", line 566, in process_eb_args
    exit_on_failure=exit_on_failure)
  File "/tmp/runner/6e8156631f16daa4203d051fabb17dbdf5c93d3b/lib/python3.6/site-packages/easybuild/main.py", line 176, in build_and_install_software
    raise EasyBuildError(test_msg)
easybuild.tools.build_log.EasyBuildError: 'Build of /tmp/eb-qmzk51pw/eb-quvkthfz/eb-r3u6w2nh/tmpz9_dvz36/toy-0.0-tweaked.eb failed (err: "build failed (first 300 chars): Failed module command detected: tclsh /home/runner/libexec/modulecmd.tcl python load toy/0.0-tweaked (stdout: _mlstatus = False\\n, stderr: Module ERROR: add-path cannot handle path equals to separator string\\n  In \'/tmp/eb-qmzk51pw/eb-quvkthfz/eb-r3u6w2nh/eb-dovnm0tg/eb-t1l3a9ua/tmpks7e57cn/all/toy/0.")'

----------------------------------------------------------------------
Ran 858 tests in 494.200s

FAILED (errors=3)
ERROR: Not all tests were successful.

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[smoors]

modules-4 does not accept : (path separator) for appending/prepending paths, and modules-3 silently fails.
it seems that "" (empty string) should also work, needs to be tested

edit: empty string does not work if the variable was not set or empty, but the following workaround works:

if {![info exists env(JULIA_DEPOT_PATH)]} {
    setenv JULIA_DEPOT_PATH :
} else {
    append-path JULIA_DEPOT_PATH {}
}