improve error message for unknown file extensions, add comment to cla…

…rify behaviour of find_extension in extract_cmd, extend test_extract_cmd to check case of unknown extension

easybuild/tools/filetools.py

@@ -1369,7 +1369,7 @@ def find_extension(filename):
     if res:
         ext = res.group('ext')
     else:
-        raise EasyBuildError('Unknown file type for file %s', filename)
+        raise EasyBuildError("%s has unknown file extension", filename)
 
     return ext
 
@@ -1382,7 +1382,9 @@ def extract_cmd(filepath, overwrite=False):
     ext = find_extension(filename)
     target = filename[:-len(ext)]
 
+    # find_extension will either return an extension listed in EXTRACT_CMDS, or raise an error
     cmd_tmpl = EXTRACT_CMDS[ext.lower()]
+
     if overwrite:
         if 'unzip -qq' in cmd_tmpl:
             cmd_tmpl = cmd_tmpl.replace('unzip -qq', 'unzip -qq -o')

test/framework/filetools.py

@@ -114,6 +114,9 @@ def test_extract_cmd(self):
 
         self.assertEqual("unzip -qq -o test.zip", ft.extract_cmd('test.zip', True))
 
+        error_pattern = "test.foo has unknown file extension"
+        self.assertErrorRegex(EasyBuildError, error_pattern, ft.extract_cmd, 'test.foo')
+
     def test_find_extension(self):
         """Test find_extension function."""
         tests = [

test/framework/toy_build.py

@@ -1368,9 +1368,6 @@ def test_toy_extension_extract_cmd(self):
         toy_ec = os.path.join(test_ecs, 't', 'toy', 'toy-0.0.eb')
         toy_ec_txt = read_file(toy_ec)
 
-        # create file that we'll copy via 'patches'
-        write_file(os.path.join(self.test_prefix, 'test.txt'), 'test123')
-
         test_ec = os.path.join(self.test_prefix, 'test.eb')
         test_ec_txt = '\n'.join([
             toy_ec_txt,