onGenerate:
org.hl7.fhir.exceptions.FHIRException: Cannot find definition for MedicationUsage
        at org.hl7.fhir.r5.renderers.ProfileDrivenRenderer.render(ProfileDrivenRenderer.java:110)
        at org.hl7.fhir.r5.renderers.ProfileDrivenRenderer.render(ProfileDrivenRenderer.java:99)
        at org.hl7.fhir.r5.renderers.ResourceRenderer.build(ResourceRenderer.java:55)
        at org.hl7.fhir.r5.renderers.BundleRenderer.render(BundleRenderer.java:298)
        at org.hl7.fhir.igtools.publisher.Publisher.getXhtml(Publisher.java:7807)
        at org.hl7.fhir.igtools.publisher.Publisher.saveDirectResourceOutputs(Publisher.java:7135)
        at org.hl7.fhir.igtools.publisher.Publisher.generateHtmlOutputs(Publisher.java:6581)
        at org.hl7.fhir.igtools.publisher.Publisher.generate(Publisher.java:4857)
        at org.hl7.fhir.igtools.publisher.Publisher.createIg(Publisher.java:881)
        at org.hl7.fhir.igtools.publisher.Publisher.execute(Publisher.java:725)
        at org.hl7.fhir.igtools.publisher.Publisher.main(Publisher.java:8335)
Generating Summary Outputs                                                       (03:37.0394)
Sending Usage Stats to Server                                                    (03:43.0322)
## Memory (MB): Use = 2103, Free = 344, Total = 2449, Max =4096
Reclaiming memory...
## Memory (MB): Use = 1367, Free = 1081, Total = 2449, Max =4096
Jekyll: /usr/local/Cellar/ruby/2.7.2/lib/ruby/2.7.0/rubygems.rb:277:in `find_spec_for_exe': can't find gem jekyll (>= 0.a) with executable jekyll (Gem::GemNotFoundException) (03:45.0345)
Jekyll: from /usr/local/Cellar/ruby/2.7.2/lib/ruby/2.7.0/rubygems.rb:296:in `activate_bin_path' (03:45.0345)
Jekyll: from /usr/local/bin/jekyll:23:in `<main>'                                (03:45.0346)
Jekyll has failed. Complete output from running Jekyll:                          (03:45.0348)
Note: Check that Jekyll is installed correctly                                   (03:45.0349)
Publishing Content Failed: Process exited with an error: 1 (Exit value: 1)       (03:45.0350)
                                                                                 (03:45.0351)
Use -? to get command line help                                                  (03:45.0351)
                                                                                 (03:45.0352)
Stack Dump (for debugging):                                                      (03:45.0352)
org.apache.commons.exec.ExecuteException: Process exited with an error: 1 (Exit value: 1)
        at org.apache.commons.exec.DefaultExecutor.executeInternal(DefaultExecutor.java:404)
        at org.apache.commons.exec.DefaultExecutor.execute(DefaultExecutor.java:166)
        at org.apache.commons.exec.DefaultExecutor.execute(DefaultExecutor.java:153)
        at org.hl7.fhir.igtools.publisher.Publisher.runJekyll(Publisher.java:5569)
        at org.hl7.fhir.igtools.publisher.Publisher.runTool(Publisher.java:5473)
        at org.hl7.fhir.igtools.publisher.Publisher.generate(Publisher.java:4919)
        at org.hl7.fhir.igtools.publisher.Publisher.createIg(Publisher.java:881)
        at org.hl7.fhir.igtools.publisher.Publisher.execute(Publisher.java:725)
        at org.hl7.fhir.igtools.publisher.Publisher.main(Publisher.java:8335)