Improve tokenization tests on primary_attr blocks

Increases the number and kind of tests run on tokenizing Primary Attribute
blocks.

tests/unit/reader/files/valid4.manifest

@@ -0,0 +1,5 @@
+# a single file block with a primary attr
+
+file "/d/e/f/g" {
+    source /a/b/c
+}

tests/unit/reader/files/valid5.manifest

@@ -0,0 +1,8 @@
+# primary_attr block, followed by non-primary_attr block
+
+manifest "man man"
+
+file {
+    source "potato"
+    target "mango"
+}

tests/unit/reader/files/valid6.manifest

@@ -0,0 +1,9 @@
+# multiple Primary Attribute style blocks
+
+manifest "man man"
+
+file "bat man"
+
+directory "super man"
+
+manifest "wo man"

tests/unit/reader/files/valid7.manifest

@@ -0,0 +1,3 @@
+# primary attr block with empty body
+
+manifest "man man" {}

tests/unit/reader/tokenize_test.py

@@ -188,6 +188,21 @@ def primary_attr_block_series():
     assert tokens[7].ty == tokenize.Token.types.TEMPLATE
 
 
+@istest
+def primary_attr_block_empty_body():
+    """
+    Unit: Tokenizer Primary Attribute Block Empty Body
+    Verifies that tokenization proceeds correctly when a "Primary Attribute"
+    style block is given a "{}" body
+    """
+    tokens = tokenize_filename(get_full_path('valid7.manifest'))
+    assert len(tokens) == 4
+    assert tokens[0].ty == tokenize.Token.types.IDENTIFIER
+    assert tokens[1].ty == tokenize.Token.types.TEMPLATE
+    assert tokens[2].ty == tokenize.Token.types.BLOCK_START
+    assert tokens[3].ty == tokenize.Token.types.BLOCK_END
+
+
 @istest
 def token_to_string():
     """