env: downgrade importlib-metadata to fix pipeline on python3.5

https://github.com/fphammerle/freesurfer-stats/commit/3e663f9ea6361988f30b83096f038b8b6ecaebe6

Pipfile

@@ -16,9 +16,12 @@ pytest-cov = "*"
 pytest-timeout = "*"
 
 # python3.5 compatibility
-# https://github.com/python/importlib_metadata/commit/107f9029fd5807c6579b881db19e11a0488f0675
 # fix pluggy/manager.py (v0.13.1) on python<3.8: import importlib_metadata => ModuleNotFoundError
-importlib-metadata = {version = "<3", markers="python_version < '3.8'"}
+# <2 for:
+# > pkg_resources.VersionConflict: (importlib-metadata 2.1.1 (/home/travis/virtualenv/python3.5.10/lib/python3.5/site-packages),
+# > Requirement.parse('importlib-metadata<2,>=0.12; python_version < "3.8"'))
+# <3 for "python_requires" https://github.com/python/importlib_metadata/commit/107f9029fd5807c6579b881db19e11a0488f0675
+importlib-metadata = {version = "<2,<3", markers="python_version < '3.8'"}
 isort = "<5"
 # workaround https://github.com/pytest-dev/pytest/issues/3953
 pathlib2 = {version = "*", markers="python_version < '3.6'"}

Pipfile.lock

@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "d6f22fde3dc0c59173a2f2fe7651e69cec3ba0ed9f88222f5db4c6440ce676a1"
+            "sha256": "88de90423e232b186c74b3af50ec7efb2d1be86acb4fe7af63ac4a839189cf79"
         },
         "pipfile-spec": 6,
         "requires": {
@@ -149,12 +149,12 @@
         },
         "importlib-metadata": {
             "hashes": [
-                "sha256:b8de9eff2b35fb037368f28a7df1df4e6436f578fa74423505b6c6a778d5b5dd",
-                "sha256:c2d6341ff566f609e89a2acb2db190e5e1d23d5409d6cc8d2fe34d72443876d4"
+                "sha256:90bb658cdbbf6d1735b6341ce708fc7024a3e14e99ffdc5783edea9f9b077f83",
+                "sha256:dc15b2969b4ce36305c51eebe62d418ac7791e9a157911d58bfb1f9ccd8e2070"
             ],
             "index": "pypi",
             "markers": "python_version < '3.8'",
-            "version": "==2.1.1"
+            "version": "==1.7.0"
         },
         "iniconfig": {
             "hashes": [