`AltConstraint` error could be more informative

[mih]

Here is the patch

diff --git a/datalad/support/constraints.py b/datalad/support/constraints.py
index 19ad29912..dd54132f5 100644
--- a/datalad/support/constraints.py
+++ b/datalad/support/constraints.py
@@ -434,8 +434,10 @@ class AltConstraints(_MultiConstraint):
                 return c(value)
             except Exception as e:
                 e_list.append(e)
-        raise ValueError("all alternative constraints (%s) violated while testing value %r"
-                         % (self.constraints, value))
+        raise ValueError(
+            f"{value} does not match any alternative: "
+            f"{self.constraints} {e_list}"
+        )
 
 

It turns:

ValueError: all alternative constraints ([constraint:<class 'list'>(constraint:path), constraint:None]) violated while testing value PosixPath('/home/mih/demo/myproject/inputs/penguins/Materials/HPP_scales_share_Final.xlsx')

into

ValueError: /home/mih/demo/myproject/inputs/penguins/Materials/HPP_scales_share_Final.xlsx does not match any alternative: [constraint:<class 'list'>(constraint:path), constraint:None] [TypeError("'PosixPath' object is not iterable"), ValueError('value must be `None`')]

It is not an option to simply raise ... from ...., because there could be more than one exception to report.

[yarikoptic-gitmate]

Issue fixed in 0.18.0