formats_err: add test for leaking enums

Tests for kaitai-io/kaitai_struct#534

Adds new failing test in compliler:

[info] - imports_enum_leaking *** FAILED ***
[info]   []
[info]     did not equal
[info]   [imports/enum_two.ksy: /seq/0/enum:
[info]          error: unable to find enum 'enum_one::one', searching from enum_two
[info]   ] (SimpleMatchers.scala:34)

formats_err/imports/enum_one.ksy

@@ -0,0 +1,10 @@
+# This is a file that is imported in imports_enum_leaking.ksy
+meta:
+  id: enum_one
+seq:
+  - id: something
+    type: u1
+    enum: one
+enums:
+  one:
+    0: zero

formats_err/imports/enum_two.ksy

@@ -0,0 +1,11 @@
+# This is a file that is imported in imports_enum_leaking.ksy
+meta:
+  id: enum_two
+  # Note: missing import of `enum_one`
+seq:
+  - id: one
+    type: u1
+    enum: enum_one::one # Note: `enum_one` is not imported in this spec, so this should cause a compile error
+enums:
+  two:
+    0: zero

formats_err/imports_enum_leaking.ksy

@@ -0,0 +1,15 @@
+# imports/enum_two.ksy: /seq/0/enum:
+# 	error: unable to find enum 'enum_one::one', searching from enum_two
+#
+meta:
+  id: imports_enum_leaking
+  imports:
+    - imports/enum_one
+    - imports/enum_two
+seq:
+  - id: another_one
+    type: u1
+    enum: enum_one::one
+  - id: another_two
+    type: u1
+    enum: enum_two::two