Fix missing dependencies in some cases

CHANGELOG.md

 # Change Log
 
+## [Unreleased]
+
+### Fixed
+
+- Fixed missing dependencies when resolving in some cases.
+
+
 ## [0.11.1] - 2018-06-29
 
 ### Fixed

poetry/puzzle/provider.py

@@ -382,6 +382,12 @@ class Provider:
                             continue
 
                         markers = pep_508_dep.split(";")[1].strip()
+                        if not markers:
+                            # One of the constraint has no markers
+                            # so this means we don't actually need to merge
+                            new_markers = []
+                            break
+
                         new_markers.append("({})".format(markers))
 
                     if not new_markers:

poetry/repositories/pypi_repository.py

@@ -275,7 +275,7 @@ class PyPiRepository(Repository):
             # dependencies by introspecting packages
             urls = {}
             for url in json_data["urls"]:
-                # Only get sdist and universal wheels
+                # Only get sdist and universal wheels if they exist
                 dist_type = url["packagetype"]
                 if dist_type not in ["sdist", "bdist_wheel"]:
                     continue
@@ -299,6 +299,23 @@ class PyPiRepository(Repository):
                     continue
 
             if not urls:
+                # If we don't have urls, we try to take the first one
+                # we find and go from there
+                if not json_data["urls"]:
+                    return data
+
+                for url in json_data["urls"]:
+                    # Only get sdist and universal wheels if they exist
+                    dist_type = url["packagetype"]
+
+                    if dist_type != "bdist_wheel":
+                        continue
+
+                    urls[url["packagetype"]] = url["url"]
+
+                    break
+
+            if not urls:
                 return data
 
             info = self._get_info_from_urls(urls)