refactor ci helper to prepare for re-use

src/_pytest/assertion/truncate.py

@@ -3,10 +3,10 @@
 Current default behaviour is to truncate assertion explanations at
 ~8 terminal lines, unless running in "-vv" mode or running on CI.
 """
-import os
 from typing import List
 from typing import Optional
 
+from _pytest.assertion import util
 from _pytest.nodes import Item
 
 
@@ -27,13 +27,7 @@ def truncate_if_required(
 def _should_truncate_item(item: Item) -> bool:
     """Whether or not this test item is eligible for truncation."""
     verbose = item.config.option.verbose
-    return verbose < 2 and not _running_on_ci()
-
-
-def _running_on_ci() -> bool:
-    """Check if we're currently running on a CI system."""
-    env_vars = ["CI", "BUILD_NUMBER"]
-    return any(var in os.environ for var in env_vars)
+    return verbose < 2 and not util.running_on_ci()
 
 
 def _truncate_explanation(

src/_pytest/assertion/util.py

@@ -1,5 +1,6 @@
 """Utilities for assertion debugging."""
 import collections.abc
+import os
 import pprint
 from typing import AbstractSet
 from typing import Any
@@ -17,7 +18,6 @@ from _pytest._io.saferepr import safeformat
 from _pytest._io.saferepr import saferepr
 from _pytest.config import Config
 
-
 # The _reprcompare attribute on the util module is used by the new assertion
 # interpretation code and assertion rewriter to detect this plugin was
 # loaded and in turn call the hooks defined here as part of the
@@ -490,3 +490,9 @@ def _notin_text(term: str, text: str, verbose: int = 0) -> List[str]:
         else:
             newdiff.append(line)
     return newdiff
+
+
+def running_on_ci() -> bool:
+    """Check if we're currently running on a CI system."""
+    env_vars = ["CI", "BUILD_NUMBER"]
+    return any(var in os.environ for var in env_vars)