Don't add un-neccesary line break in grouped vertical grid.

Prior to this change, isort was always adding 1 to the current line length when
determining whether or not the current line had got too long when outputting a
vertical grid.

- For imports that are not last, this is fine.  We need to account for the comma
  after the import.
- For the final import in vertical grid mode this is also fine.  We need to
  account for the closing `)`.
- For the final import in the grouped vertical grid we put the closing ) on the
  next line, so adding 1 to the line length causes isort to add un-neccesary
  line breaks when the final import would only just fit onto the line by one
  character.

For example, with a line length of 20:

```
from x import (
    abcd, efgh, ijkl
)
```

will end up reformatted as

```
from x import (
    abcd, efgh,
    ijkl
)
```

This is causing problems for us, as we run yapf on our code as well as isort,
and our imports change depending on which tool ran last.

1 files changed, 10 insertions, 0 deletions

diff --git a/test_isort.py b/test_isort.py
index de4f8c9c..5e4e179a 100644
--- a/test_isort.py
+++ b/test_isort.py
@@ -36,6 +36,8 @@ SHORT_IMPORT = "from third_party import lib1, lib2, lib3, lib4"
 
 SINGLE_FROM_IMPORT = "from third_party import lib1"
 
+SINGLE_LINE_LONG_IMPORT = "from third_party import lib1, lib2, lib3, lib4, lib5, lib5ab"
+
 REALLY_LONG_IMPORT = ("from third_party import lib1, lib2, lib3, lib4, lib5, lib6, lib7, lib8, lib9, lib10, lib11,"
                       "lib12, lib13, lib14, lib15, lib16, lib17, lib18, lib20, lib21, lib22")
 REALLY_LONG_IMPORT_WITH_COMMENT = ("from third_party import lib1, lib2, lib3, lib4, lib5, lib6, lib7, lib8, lib9, "
@@ -352,6 +354,14 @@ def test_output_modes():
                               multi_line_output=WrapModes.NOQA).output
     assert output_noqa == "from third_party import lib1, lib2, lib3, lib4, lib5, lib6, lib7, lib8, lib9, lib10, lib11, lib12, lib13, lib14, lib15, lib16, lib17, lib18, lib20, lib21, lib22  # NOQA comment\n"  # NOQA
 
+    test_output_vertical_grid_grouped_doesnt_wrap_early = SortImports(file_contents=SINGLE_LINE_LONG_IMPORT,
+                                                                      multi_line_output=WrapModes.VERTICAL_GRID_GROUPED,
+                                                                      line_length=40, indent='    ').output
+    assert test_output_vertical_grid_grouped_doesnt_wrap_early == ("from third_party import (\n"
+                                                                   "    lib1, lib2, lib3, lib4, lib5, lib5ab\n"
+                                                                   ")\n")
+
+
 
 def test_qa_comment_case():
     test_input = "from veryveryveryveryveryveryveryveryveryveryvery import X  # NOQA"