[core] Add ProcessEnv class in new plugins module

Add a new module named `plugins` with a `ProcessEnv` class which
contains the paths describing the environment needed for the plugin's
(node's) process.

meshroom/core/__init__.py

@@ -19,6 +19,7 @@ try:
 except Exception:
     pass
 
+from meshroom.core.plugins import ProcessEnv
 from meshroom.core.submitter import BaseSubmitter
 from meshroom.env import EnvVar, meshroomFolder
 from . import desc
@@ -349,9 +350,7 @@ def loadPluginFolder(folder):
         logging.info(f"Plugin folder '{folder}' does not contain a 'meshroom' folder.")
         return
 
-    binFolders = [Path(folder, 'bin')]
-    libFolders = [Path(folder, 'lib'), Path(folder, 'lib64')]
-    pythonPathFolders = [Path(folder)] + binFolders
+    processEnv = ProcessEnv(folder)
 
     loadAllNodes(folder=mrFolder)
     loadPipelineTemplates(folder=mrFolder)

meshroom/core/plugins.py

@@ -0,0 +1,14 @@
+from pathlib import Path
+
+from meshroom.common import BaseObject
+
+class ProcessEnv(BaseObject):
+    """
+    Describes the environment required by a node's process.
+    """
+
+    def __init__(self, folder: str):
+        super().__init__()
+        self.binPaths: list = [Path(folder, "bin")]
+        self.libPaths: list = [Path(folder, "lib"), Path(folder, "lib64")]
+        self.pythonPathFolders: list = [Path(folder)] + self.binPaths