`mazer install alikins.collection_reqs_test,version='^2.0.0'` throws ValueError

[alikins]

Bug Report

(mazer040test) [newswoop:F29:collection_reqs_test (master % u=)]$ rm -rf /tmp/coltest2/* && mazer install --collections-path=/tmp/coltest2 --server http://localhost:8000 alikins.collection_reqs_test,version=^2.0.0
Invalid requirement specification: '==^2.0.0'
Traceback (most recent call last):
  File "/home/adrian/venvs/mazer040test/bin/mazer", line 11, in <module>
    load_entry_point('mazer', 'console_scripts', 'mazer')()
  File "/home/adrian/src/mazer/ansible_galaxy_cli/main.py", line 36, in main
    exit_code = cli.run()
  File "/home/adrian/src/mazer/ansible_galaxy_cli/cli/galaxy.py", line 217, in run
    return self.execute()
  File "/home/adrian/src/mazer/ansible_galaxy_cli/cli/__init__.py", line 152, in execute
    return fn()
  File "/home/adrian/src/mazer/ansible_galaxy_cli/cli/galaxy.py", line 283, in execute_install
    force_overwrite=self.options.force)
  File "/home/adrian/src/mazer/ansible_galaxy/actions/install.py", line 144, in install_repository_specs_loop
    req_spec = RequirementSpec.from_dict(spec_data)
  File "/home/adrian/src/mazer/ansible_galaxy/models/requirement_spec.py", line 66, in from_dict
    src=data.get('src', None),
  File "<attrs generated init 5efb205521f1ae1d547415b47c1cac28c8c822e6>", line 5, in __init__
  File "/home/adrian/src/mazer/ansible_galaxy/utils/version.py", line 32, in convert_string_to_version_spec
    return semantic_version.Spec(version_spec)
  File "/home/adrian/venvs/mazer040test/lib/python3.6/site-packages/semantic_version/base.py", line 505, in __init__
    subspecs = [self.parse(spec) for spec in specs_strings]
  File "/home/adrian/venvs/mazer040test/lib/python3.6/site-packages/semantic_version/base.py", line 505, in <listcomp>
    subspecs = [self.parse(spec) for spec in specs_strings]
  File "/home/adrian/venvs/mazer040test/lib/python3.6/site-packages/semantic_version/base.py", line 511, in parse
    return tuple(SpecItem(spec_text) for spec_text in spec_texts)
  File "/home/adrian/venvs/mazer040test/lib/python3.6/site-packages/semantic_version/base.py", line 511, in <genexpr>
    return tuple(SpecItem(spec_text) for spec_text in spec_texts)
  File "/home/adrian/venvs/mazer040test/lib/python3.6/site-packages/semantic_version/base.py", line 425, in __init__
    kind, spec = self.parse(requirement_string)
  File "/home/adrian/venvs/mazer040test/lib/python3.6/site-packages/semantic_version/base.py", line 440, in parse
    raise ValueError("Invalid requirement specification: %r" % requirement_string)
ValueError: Invalid requirement specification: '==^2.0.0'

MAZER VERSION

git devel 1fa2cbe5b5c6247230230faed721d81c8c78d1f9

name = mazer
version = 0.4.0
config_file = /home/adrian/.ansible/mazer.yml
uname = Linux, newswoop, 5.0.5-200.fc29.x86_64, #1 SMP Wed Mar 27 20:58:04 UTC 2019, x86_64
executable_location = /home/adrian/venvs/mazer040test/bin/mazer
python_version = 3.6.8 (default, Jan 27 2019, 09:00:23) [GCC 8.2.1 20181215 (Red Hat 8.2.1-6)]
python_executable = /home/adrian/venvs/mazer040test/bin/python

CONFIGURATION

SUMMARY

STEPS TO REPRODUCE

EXPECTED RESULTS

ACTUAL RESULTS