fix: use conda package version parsing by obtaining conda version spe…

…c from github (#52)

README.md

@@ -17,3 +17,4 @@ For getting started and a basic tutorial, see the documentation at
 ## License
 
  * Free software: MPL 2.0 License
+ * `snakedeploy/conda_version.py`: the [source](https://github.com/conda/conda/raw/23.1.0/conda/models/version.py) of this file is distributed under the BSD 3-clause license by Anaconda Inc.

setup.py

@@ -8,6 +8,7 @@
 from setuptools import setup, find_packages
 import versioneer
 import os
+import urllib.request
 
 
 def get_lookup():

snakedeploy/conda.py

@@ -19,6 +19,7 @@
 from snakedeploy.exceptions import UserError
 from snakedeploy.logger import logger
 from snakedeploy.utils import YamlDumper
+from snakedeploy.conda_version import VersionOrder
 
 
 def pin_conda_envs(conda_env_paths: list, conda_frontend="mamba"):
@@ -193,16 +194,14 @@ def get_pkg_versions(conda_env_path):
         def downgraded():
             for pkg_name, version in posterior_pkg_versions.items():
                 try:
-                    version = packaging_version.parse(version)
+                    version = VersionOrder(version)
                 except packaging_version.InvalidVersion as e:
                     logger.debug(json.dumps(posterior_pkg_json, indent=2))
                     raise UserError(
                         f"Cannot parse version {version} of package {pkg_name}: {e}"
                     )
                 prior_version = prior_pkg_versions.get(pkg_name)
-                if prior_version is not None and version < packaging_version.parse(
-                    prior_version
-                ):
+                if prior_version is not None and version < VersionOrder(prior_version):
                     yield pkg_name
 
         downgraded = list(downgraded())