Cleanup: Move package download/install code out of subproc.py

Instead do such things in bpkg, and only handle interfacing between
blender and bpkg in subproc.py

package_manager/messages.py

@@ -27,38 +27,6 @@ class Progress(SubprocMessage):
     def __init__(self, progress: float):
         self.progress = progress
 
-class SubprocError(SubprocMessage):
-    """Superclass for all fatal error messages sent from the subprocess."""
-
-    def __init__(self, message: str):
-        self.message = message
-
-class SubprocWarning(SubprocMessage):
-    """Superclass for all non-fatal warning messages sent from the subprocess."""
-
-    def __init__(self, message: str):
-        self.message = message
-
-class InstallError(SubprocError):
-    """Sent when there was an error installing something."""
-
-class UninstallError(SubprocError):
-    """Sent when there was an error uninstalling something."""
-
-class FileConflictError(InstallError):
-    """Sent when installation would overwrite existing files."""
-
-    def __init__(self, message: str, conflicts: list):
-        self.message = message
-        self.conflicts = conflicts
-
-class DownloadError(SubprocMessage):
-    """Sent when there was an error downloading something."""
-
-    def __init__(self, status_code: int, description: str):
-        self.status_code = status_code
-        self.description = description
-
 class Success(SubprocMessage):
     """Sent when an operation finished sucessfully."""
 
@@ -71,3 +39,35 @@ class RepositoryResult(SubprocMessage):
 class Aborted(SubprocMessage):
     """Sent as response to Abort message."""
 
+# subproc warnings
+
+class SubprocWarning(SubprocMessage):
+    """Superclass for all non-fatal warning messages sent from the subprocess."""
+
+    def __init__(self, message: str):
+        self.message = message
+
+# subproc errors
+
+class SubprocError(SubprocMessage):
+    """Superclass for all fatal error messages sent from the subprocess."""
+
+    def __init__(self, message: str):
+        self.message = message
+
+class InstallError(SubprocError):
+    """Sent when there was an error installing something."""
+
+class UninstallError(SubprocError):
+    """Sent when there was an error uninstalling something."""
+
+class BadRepositoryError(SubprocError):
+    """Sent when a repository can't be used for some reason"""
+
+class DownloadError(SubprocMessage):
+    """Sent when there was an error downloading something."""
+
+    def __init__(self, message: str, status_code: int = None):
+        self.status_code = status_code
+        self.message = message
+