Adds new lint function for empty env files

New function that raises a failure if the size of
the environment file, if this one exists, is zero.

Signed-off-by: mcasquer <[email protected]>

tmt/base.py

@@ -2130,6 +2130,21 @@ def lint_unknown_keys(self) -> LinterReturn:
 
         yield LinterOutcome.PASS, 'correct keys are used'
 
+    def lint_empty_env_files(self) -> LinterReturn:
+        """ P001: env files are not empty """
+
+        env_files = self.node.get("environment-file") or []
+        if env_files:
+            for env_file in env_files:
+                env_file = Path(env_file).resolve()
+
+                if not env_file.exists() or not env_file.stat().st_size:
+                    yield LinterOutcome.FAIL, f'the file "{env_file}" does not exists or is empty'
+
+                    return
+
+        yield LinterOutcome.PASS, 'no empty environment files found'
+
     def lint_execute_not_defined(self) -> LinterReturn:
         """ P002: execute step must be defined with "how" """