Add explicit dependency on black formatter tool

Change-Id: Ibe58f15d46fbeab984738971e849801c7cd55f55
diff --git a/Pipfile b/Pipfile
index 437dc0a..7892752 100644
--- a/Pipfile
+++ b/Pipfile
@@ -11,6 +11,10 @@
 [dev-packages]
 flake8 = "==3.5.0"
 pyflakes = "==1.6.0"
+black = {version = "==19.10b0", markers = "python_version >= '3.6.0'"}
 
 [requires]
 python_version = "3.7"
+
+[pipenv]
+allow_prereleases = true
diff --git a/Pipfile.lock b/Pipfile.lock
index 302ed16..5489c58 100644
--- a/Pipfile.lock
+++ b/Pipfile.lock
@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "fcc9c1b10e5be30f882b75a9028bd98b3c620556246bbc3d1cb24a22f07daa25"
+            "sha256": "349c040d335d7c31282d4a10981ae5a6ff6c228f1e7d6ea75557360cfd07dc03"
         },
         "pipfile-spec": 6,
         "requires": {
@@ -116,6 +116,36 @@
         }
     },
     "develop": {
+        "appdirs": {
+            "hashes": [
+                "sha256:9e5896d1372858f8dd3344faf4e5014d21849c756c8d5701f78f8a103b372d92",
+                "sha256:d8b24664561d0d34ddfaec54636d502d7cea6e29c3eaf68f3df6180863e2166e"
+            ],
+            "version": "==1.4.3"
+        },
+        "attrs": {
+            "hashes": [
+                "sha256:08a96c641c3a74e44eb59afb61a24f2cb9f4d7188748e76ba4bb5edfa3cb7d1c",
+                "sha256:f7b7ce16570fe9965acd6d30101a28f62fb4a7f9e926b3bbc9b61f8b04247e72"
+            ],
+            "version": "==19.3.0"
+        },
+        "black": {
+            "hashes": [
+                "sha256:1b30e59be925fafc1ee4565e5e08abef6b03fe455102883820fe5ee2e4734e0b",
+                "sha256:c2edb73a08e9e0e6f65a0e6af18b059b8b1cdd5bef997d7a0b181df93dc81539"
+            ],
+            "index": "pypi",
+            "markers": "python_version >= '3.6.0'",
+            "version": "==19.10b0"
+        },
+        "click": {
+            "hashes": [
+                "sha256:2335065e6395b9e67ca716de5f7526736bfa6ceead690adf616d925bdc622b13",
+                "sha256:5b94b49521f6456670fdb30cd82a4eca9412788a93fa6dd6df72c94d5a8ff2d7"
+            ],
+            "version": "==7.0"
+        },
         "flake8": {
             "hashes": [
                 "sha256:7253265f7abd8b313e3892944044a365e3f4ac3fcdcfb4298f55ee9ddf188ba0",
@@ -131,6 +161,13 @@
             ],
             "version": "==0.6.1"
         },
+        "pathspec": {
+            "hashes": [
+                "sha256:981f9323b6830b7da56a6b4aac3a63646495b8043db06ad2d40fd1cb32b90830",
+                "sha256:e285ccc8b0785beadd4c18e5708b12bb8fcf529a1e61215b3feff1d1e559ea5c"
+            ],
+            "version": "==0.6.0"
+        },
         "pycodestyle": {
             "hashes": [
                 "sha256:682256a5b318149ca0d2a9185d365d8864a768a28db66a84a2ea946bcc426766",
@@ -145,6 +182,54 @@
             ],
             "index": "pypi",
             "version": "==1.6.0"
+        },
+        "regex": {
+            "hashes": [
+                "sha256:15454b37c5a278f46f7aa2d9339bda450c300617ca2fca6558d05d870245edc7",
+                "sha256:1ad40708c255943a227e778b022c6497c129ad614bb7a2a2f916e12e8a359ee7",
+                "sha256:5e00f65cc507d13ab4dfa92c1232d004fa202c1d43a32a13940ab8a5afe2fb96",
+                "sha256:604dc563a02a74d70ae1f55208ddc9bfb6d9f470f6d1a5054c4bd5ae58744ab1",
+                "sha256:720e34a539a76a1fedcebe4397290604cc2bdf6f81eca44adb9fb2ea071c0c69",
+                "sha256:7caf47e4a9ac6ef08cabd3442cc4ca3386db141fb3c8b2a7e202d0470028e910",
+                "sha256:c31eaf28c6fe75ea329add0022efeed249e37861c19681960f99bbc7db981fb2",
+                "sha256:c7393597191fc2043c744db021643549061e12abe0b3ff5c429d806de7b93b66",
+                "sha256:d2b302f8cdd82c8f48e9de749d1d17f85ce9a0f082880b9a4859f66b07037dc6",
+                "sha256:e3d8dd0ec0ea280cf89026b0898971f5750a7bd92cb62c51af5a52abd020054a",
+                "sha256:ec032cbfed59bd5a4b8eab943c310acfaaa81394e14f44454ad5c9eba4f24a74"
+            ],
+            "version": "==2019.11.1"
+        },
+        "toml": {
+            "hashes": [
+                "sha256:229f81c57791a41d65e399fc06bf0848bab550a9dfd5ed66df18ce5f05e73d5c",
+                "sha256:235682dd292d5899d361a811df37e04a8828a5b1da3115886b73cf81ebc9100e"
+            ],
+            "version": "==0.10.0"
+        },
+        "typed-ast": {
+            "hashes": [
+                "sha256:1170afa46a3799e18b4c977777ce137bb53c7485379d9706af8a59f2ea1aa161",
+                "sha256:18511a0b3e7922276346bcb47e2ef9f38fb90fd31cb9223eed42c85d1312344e",
+                "sha256:262c247a82d005e43b5b7f69aff746370538e176131c32dda9cb0f324d27141e",
+                "sha256:2b907eb046d049bcd9892e3076c7a6456c93a25bebfe554e931620c90e6a25b0",
+                "sha256:354c16e5babd09f5cb0ee000d54cfa38401d8b8891eefa878ac772f827181a3c",
+                "sha256:48e5b1e71f25cfdef98b013263a88d7145879fbb2d5185f2a0c79fa7ebbeae47",
+                "sha256:4e0b70c6fc4d010f8107726af5fd37921b666f5b31d9331f0bd24ad9a088e631",
+                "sha256:630968c5cdee51a11c05a30453f8cd65e0cc1d2ad0d9192819df9978984529f4",
+                "sha256:66480f95b8167c9c5c5c87f32cf437d585937970f3fc24386f313a4c97b44e34",
+                "sha256:71211d26ffd12d63a83e079ff258ac9d56a1376a25bc80b1cdcdf601b855b90b",
+                "sha256:7954560051331d003b4e2b3eb822d9dd2e376fa4f6d98fee32f452f52dd6ebb2",
+                "sha256:838997f4310012cf2e1ad3803bce2f3402e9ffb71ded61b5ee22617b3a7f6b6e",
+                "sha256:95bd11af7eafc16e829af2d3df510cecfd4387f6453355188342c3e79a2ec87a",
+                "sha256:bc6c7d3fa1325a0c6613512a093bc2a2a15aeec350451cbdf9e1d4bffe3e3233",
+                "sha256:cc34a6f5b426748a507dd5d1de4c1978f2eb5626d51326e43280941206c209e1",
+                "sha256:d755f03c1e4a51e9b24d899561fec4ccaf51f210d52abdf8c07ee2849b212a36",
+                "sha256:d7c45933b1bdfaf9f36c579671fec15d25b06c8398f113dab64c18ed1adda01d",
+                "sha256:d896919306dd0aa22d0132f62a1b78d11aaf4c9fc5b3410d3c666b818191630a",
+                "sha256:fdc1c9bbf79510b76408840e009ed65958feba92a88833cdceecff93ae8fff66",
+                "sha256:ffde2fbfad571af120fcbfbbc61c72469e72f550d676c3342492a9dfdefb8f12"
+            ],
+            "version": "==1.4.0"
         }
     }
 }