Improve error message (#9624)

* Improve error message

Otherwise this would only print  "ERROR: True"

* add test

Co-authored-by: memsharded <james@conan.io>

2 files changed, 18 insertions, 1 deletions

diff --git a/conans/client/graph/graph_builder.py b/conans/client/graph/graph_builder.py
index f55d54ee..9f9d3baa 100644
--- a/conans/client/graph/graph_builder.py
+++ b/conans/client/graph/graph_builder.py
@@ -328,7 +328,8 @@ class DepsGraphBuilder(object):
                         "in your root package."
                         % (consumer_ref, consumer_ref, new_ref, next(iter(previous.dependants)).src,
                            previous.ref, new_ref.name))
-            return True
+            return "Unresolvable conflict between {} and {}".format(previous.ref, new_ref)
+
         # Computed node, if is Editable, has revision=None
         # If new_ref.revision is None we cannot assume any conflict, the user hasn't specified
         # a revision, so it's ok any previous_ref
diff --git a/conans/test/integration/graph/conflict_diamond_test.py b/conans/test/integration/graph/conflict_diamond_test.py
index 998c3833..476c6c1d 100644
--- a/conans/test/integration/graph/conflict_diamond_test.py
+++ b/conans/test/integration/graph/conflict_diamond_test.py
@@ -4,6 +4,7 @@ import unittest
 
 from conans.client.tools import environment_append
 from conans.paths import CONANFILE
+from conans.test.assets.genconanfile import GenConanfile
 from conans.test.utils.tools import TestClient, load
 import json
 
@@ -97,3 +98,18 @@ class ConflictDiamondTest(unittest.TestCase):
             self.assertEqual(hello0["reference"], "Hello0/0.1@lasote/stable")
             self.assertListEqual(sorted(hello0["required_by"]),
                                  sorted(["Hello2/0.1@lasote/stable", "Hello1/0.1@lasote/stable"]))
+
+
+def test_conflict_msg():
+    c = TestClient()
+    c.save({"lib/conanfile.py": GenConanfile(),
+            "conanfile.txt":  textwrap.dedent("""
+                                [requires]
+                                libdeflate/1.7
+                                [build_requires]
+                                libdeflate/1.8
+                                """)})
+    c.run("export lib libdeflate/1.7@")
+    c.run("export lib libdeflate/1.8@")
+    c.run("install .", assert_error=True)
+    assert "ERROR: Unresolvable conflict between libdeflate/1.7 and libdeflate/1.8" in c.out