parse_specifier_for_install: using abs path for constraint and requirements

Author: guysalt

changelog.d/1389.bugfix.md

@@ -0,0 +1 @@
+Fix error with `pipx install` Command Using Relative Path for Pip Arguments

src/pipx/package_specifier.py

@@ -161,7 +161,22 @@ def parse_specifier_for_install(package_spec: str, pip_args: List[str]) -> Tuple
         )
         pip_args.remove("--editable")
 
-    return (package_or_url, pip_args)
+    pip_args = [option for pip_arg in pip_args for option in pip_arg.split(" ")]
+
+    for option in pip_args:
+        if "-c" in option or "--constraint" in option:
+            option_list = option.split("=")
+
+            if len(option_list) != 2:
+                continue
+
+            key, value = option_list
+            value_path = Path(value).expanduser().resolve()
+            pip_args[pip_args.index(option)] = f"{key}={value_path}"
+
+            break
+
+    return package_or_url, pip_args
 
 
 def parse_specifier_for_metadata(package_spec: str) -> str: