Move the warnings/errors in a place that doesn't import anything.

src/pytest_cov/__init__.py

@@ -1,3 +1,47 @@
 """pytest-cov: avoid already-imported warning: PYTEST_DONT_REWRITE."""
 
 __version__ = '5.0.0'
+
+import pytest
+
+
+class CoverageError(Exception):
+    """Indicates that our coverage is too low"""
+
+
+class PytestCovWarning(pytest.PytestWarning):
+    """
+    The base for all pytest-cov warnings, never raised directly.
+    """
+
+
+class CovDisabledWarning(PytestCovWarning):
+    """
+    Indicates that Coverage was manually disabled.
+    """
+
+
+class CovReportWarning(PytestCovWarning):
+    """
+    Indicates that we failed to generate a report.
+    """
+
+
+class CovFailUnderWarning(PytestCovWarning):
+    """
+    Indicates that we failed to generate a report.
+    """
+
+
+class CentralCovContextWarning(PytestCovWarning):
+    """
+    Indicates that dynamic_context was set to test_function instead of using the builtin --cov-context.
+    """
+
+
+class DistCovError(Exception):
+    """
+    Raised when dynamic_context is set to test_function and xdist is also used.
+
+    See: https://github.com/pytest-dev/pytest-cov/issues/604
+    """

src/pytest_cov/engine.py

@@ -15,8 +15,9 @@
 from coverage.data import CoverageData
 from coverage.sqldata import filename_suffix
 
+from . import CentralCovContextWarning
+from . import DistCovError
 from .embed import cleanup
-from .plugin import PytestCovWarning
 
 
 class BrokenCovConfigError(Exception):
@@ -231,10 +232,6 @@ def summary(self, stream):
         return total
 
 
-class CentralCovContextWarning(PytestCovWarning):
-    pass
-
-
 class Central(CovController):
     """Implementation for centralised operation."""
 
@@ -286,10 +283,6 @@ def finish(self):
         self.node_descs.add(node_desc)
 
 
-class DistCovError(Exception):
-    pass
-
-
 class DistMaster(CovController):
     """Implementation for distributed master."""
 

src/pytest_cov/plugin.py

@@ -11,32 +11,13 @@
 from coverage.results import display_covered
 from coverage.results import should_fail_under
 
+from . import CovDisabledWarning
+from . import CovFailUnderWarning
+from . import CovReportWarning
 from . import compat
 from . import embed
 
 
-class CoverageError(Exception):
-    """Indicates that our coverage is too low"""
-
-
-class PytestCovWarning(pytest.PytestWarning):
-    """
-    The base for all pytest-cov warnings, never raised directly
-    """
-
-
-class CovDisabledWarning(PytestCovWarning):
-    """Indicates that Coverage was manually disabled"""
-
-
-class CovReportWarning(PytestCovWarning):
-    """Indicates that we failed to generate a report"""
-
-
-class CovFailUnderWarning(PytestCovWarning):
-    """Indicates that we failed to generate a report"""
-
-
 def validate_report(arg):
     file_choices = ['annotate', 'html', 'xml', 'json', 'lcov']
     term_choices = ['term', 'term-missing']

tests/test_pytest_cov.py

@@ -1674,7 +1674,7 @@ def test_dynamic_context(pytester, testdir, opts, prop):
 """)
     result = testdir.runpytest('-v', f'--cov={script.dirpath()}', script, *opts.split() + prop.args)
     if opts:
-        result.stderr.fnmatch_lines(['pytest_cov.engine.DistCovError: Detected dynamic_context=test_function*'])
+        result.stderr.fnmatch_lines(['pytest_cov.DistCovError: Detected dynamic_context=test_function*'])
     else:
         result.stdout.fnmatch_lines(
             [