black: fix format-sensitive tests

Some of our tests rely on single vs. double quotes, and others rely on specific
line numbers in the source. These needed fixing after the switch to Black.

lib/spack/spack/test/cmd/blame.py

@@ -77,4 +77,4 @@ def test_blame_by_git(mock_packages, capfd):
     with capfd.disabled():
         out = blame("--git", "mpich")
     assert "class Mpich" in out
-    assert '    homepage   = "http://www.mpich.org"' in out
+    assert '    homepage = "http://www.mpich.org"' in out

lib/spack/spack/test/cmd/pkg.py

@@ -254,7 +254,7 @@ def test_pkg_source(mock_packages):
 
 def test_pkg_canonical_source(mock_packages):
     source = pkg("source", "multimethod")
-    assert "@when('@2.0')" in source
+    assert '@when("@2.0")' in source
     assert "Check that multimethods work with boolean values" in source
 
     canonical_1 = pkg("source", "--canonical", "multimethod@1.0")

lib/spack/spack/test/llnl/util/lang.py

@@ -306,16 +306,16 @@ def inner():
     due to the following failures:
     inner method raised ValueError: wow!
       File "{0}", \
-line 283, in test_grouped_exception
+line 290, in test_grouped_exception
         inner()
       File "{0}", \
-line 280, in inner
-        raise ValueError('wow!')
+line 287, in inner
+        raise ValueError("wow!")
 
     top-level raised TypeError: ok
       File "{0}", \
-line 286, in test_grouped_exception
-        raise TypeError('ok')
+line 293, in test_grouped_exception
+        raise TypeError("ok")
     """
         ).format(__file__)
     )