Rewrite invalid imports checker to Python

Makes it consistent with other checkers we already have

scripts/check_invalid_imports.py

@@ -0,0 +1,60 @@
+import os
+import re
+import sys
+from pathlib import Path
+
+"""
+Run this file with the Cura project root as the working directory
+"""
+
+class InvalidImportsChecker:
+    # compile regex
+    REGEX = re.compile(r"^\s*(from plugins|import plugins)")
+
+    def check(self):
+        """ Checks for invalid imports
+
+        :return: True if checks passed, False when the test fails
+        """
+        cwd = os.getcwd()
+        cura_result = checker.check_dir(os.path.join(cwd, "cura"))
+        plugins_result = checker.check_dir(os.path.join(cwd, "plugins"))
+        result = cura_result and plugins_result
+        if not result:
+            print("error: sources contain invalid imports. Use relative imports when referencing plugin source files")
+
+        return result
+
+    def check_dir(self, root_dir: str) -> bool:
+        """ Checks a directory for invalid imports
+
+        :return: True if checks passed, False when the test fails
+        """
+        passed = True
+        for path_like in Path(root_dir).rglob('*.py'):
+            if not self.check_file(str(path_like)):
+                passed = False
+
+        return passed
+
+    def check_file(self, file_path):
+        """ Checks a file for invalid imports
+
+        :return: True if checks passed, False when the test fails
+        """
+        passed = True
+        with open(file_path, 'r', encoding = "utf-8") as inputFile:
+            # loop through each line in file
+            for line_i, line in enumerate(inputFile, 1):
+                # check if we have a regex match
+                match = self.REGEX.search(line)
+                if match:
+                    path = os.path.relpath(file_path)
+                    print("{path}:{line_i}:{match}".format(path=path, line_i=line_i, match=match.group(1)))
+                    passed = False
+        return passed
+
+
+if __name__ == "__main__":
+    checker = InvalidImportsChecker()
+    sys.exit(0 if checker.check() else 1)